NORTHWESTERN CORPORATION has sponsored the creation of one or more 401k plans.
Submission information for form 5500 for 401k plan NORTHWESTERN ENERGY MASTER RETIREMENT TRUST
| Measure | Date | Value |
|---|
| 2023 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2023 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2023-12-31 | $0 |
| Total transfer of assets to this plan | 2023-12-31 | $9,200,000 |
| Total transfer of assets from this plan | 2023-12-31 | $83,466,111 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2023-12-31 | $170,576 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2023-12-31 | $400,863 |
| Total income from all sources (including contributions) | 2023-12-31 | $36,495,396 |
| Total loss/gain on sale of assets | 2023-12-31 | $1 |
| Total of all expenses incurred | 2023-12-31 | $867,413 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2023-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2023-12-31 | $0 |
| Value of total assets at end of year | 2023-12-31 | $402,670,966 |
| Value of total assets at beginning of year | 2023-12-31 | $441,539,381 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2023-12-31 | $867,413 |
| Total interest from all sources | 2023-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2023-12-31 | $0 |
| Were there any nonexempt tranactions with any party-in-interest | 2023-12-31 | No |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2023-12-31 | $5,158 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2023-12-31 | $3,402 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2023-12-31 | $170,576 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2023-12-31 | $400,863 |
| Value of net income/loss | 2023-12-31 | $35,627,983 |
| Value of net assets at end of year (total assets less liabilities) | 2023-12-31 | $402,500,390 |
| Value of net assets at beginning of year (total assets less liabilities) | 2023-12-31 | $441,138,518 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2023-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2023-12-31 | No |
| Investment advisory and management fees | 2023-12-31 | $760,088 |
| Value of interest in common/collective trusts at end of year | 2023-12-31 | $402,665,808 |
| Value of interest in common/collective trusts at beginning of year | 2023-12-31 | $441,535,979 |
| Net investment gain or loss from common/collective trusts | 2023-12-31 | $36,495,395 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2023-12-31 | Yes |
| Did the plan have assets held for investment | 2023-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2023-12-31 | $1 |
| Total unrealized appreciation/depreciation of assets | 2023-01-01 | $0 |
| Total transfer of assets to this plan | 2023-01-01 | $9,200,000 |
| Total transfer of assets from this plan | 2023-01-01 | $83,466,111 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2023-01-01 | $170,576 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2023-01-01 | $400,863 |
| Total income from all sources (including contributions) | 2023-01-01 | $36,495,396 |
| Total loss/gain on sale of assets | 2023-01-01 | $1 |
| Total of all expenses incurred | 2023-01-01 | $867,413 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2023-01-01 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2023-01-01 | $0 |
| Value of total assets at end of year | 2023-01-01 | $402,670,966 |
| Value of total assets at beginning of year | 2023-01-01 | $441,539,381 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2023-01-01 | $867,413 |
| Total interest from all sources | 2023-01-01 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2023-01-01 | $0 |
| Were there any nonexempt tranactions with any party-in-interest | 2023-01-01 | No |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2023-01-01 | $5,158 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2023-01-01 | $3,402 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2023-01-01 | $170,576 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2023-01-01 | $400,863 |
| Value of net income/loss | 2023-01-01 | $35,627,983 |
| Value of net assets at end of year (total assets less liabilities) | 2023-01-01 | $402,500,390 |
| Value of net assets at beginning of year (total assets less liabilities) | 2023-01-01 | $441,138,518 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2023-01-01 | No |
| Were any leases to which the plan was party in default or uncollectible | 2023-01-01 | No |
| Investment advisory and management fees | 2023-01-01 | $760,088 |
| Value of interest in common/collective trusts at end of year | 2023-01-01 | $402,665,808 |
| Value of interest in common/collective trusts at beginning of year | 2023-01-01 | $441,535,979 |
| Net investment gain or loss from common/collective trusts | 2023-01-01 | $36,495,395 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2023-01-01 | Yes |
| Did the plan have assets held for investment | 2023-01-01 | Yes |
| Aggregate proceeds on sale of assets | 2023-01-01 | $1 |
| 2022 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2022 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2022-12-31 | $0 |
| Total transfer of assets to this plan | 2022-12-31 | $8,839,600 |
| Total transfer of assets from this plan | 2022-12-31 | $28,580,573 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2022-12-31 | $400,863 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2022-12-31 | $649,647 |
| Total income from all sources (including contributions) | 2022-12-31 | $-142,980,230 |
| Total loss/gain on sale of assets | 2022-12-31 | $140 |
| Total of all expenses incurred | 2022-12-31 | $989,821 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2022-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2022-12-31 | $0 |
| Value of total assets at end of year | 2022-12-31 | $441,539,381 |
| Value of total assets at beginning of year | 2022-12-31 | $605,499,189 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2022-12-31 | $989,821 |
| Total interest from all sources | 2022-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2022-12-31 | $0 |
| Administrative expenses professional fees incurred | 2022-12-31 | $119,851 |
| Were there any nonexempt tranactions with any party-in-interest | 2022-12-31 | No |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2022-12-31 | $3,402 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2022-12-31 | $18 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2022-12-31 | $400,863 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2022-12-31 | $649,647 |
| Value of net income/loss | 2022-12-31 | $-143,970,051 |
| Value of net assets at end of year (total assets less liabilities) | 2022-12-31 | $441,138,518 |
| Value of net assets at beginning of year (total assets less liabilities) | 2022-12-31 | $604,849,542 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2022-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2022-12-31 | No |
| Investment advisory and management fees | 2022-12-31 | $869,970 |
| Value of interest in common/collective trusts at end of year | 2022-12-31 | $441,535,979 |
| Value of interest in common/collective trusts at beginning of year | 2022-12-31 | $605,499,171 |
| Net investment gain or loss from common/collective trusts | 2022-12-31 | $-142,980,370 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2022-12-31 | Yes |
| Did the plan have assets held for investment | 2022-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2022-12-31 | $140 |
| Total unrealized appreciation/depreciation of assets | 2022-01-01 | $0 |
| Total transfer of assets to this plan | 2022-01-01 | $8,839,600 |
| Total transfer of assets from this plan | 2022-01-01 | $-28,580,573 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2022-01-01 | $400,863 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2022-01-01 | $649,647 |
| Total income from all sources (including contributions) | 2022-01-01 | $-142,980,230 |
| Total loss/gain on sale of assets | 2022-01-01 | $140 |
| Total of all expenses incurred | 2022-01-01 | $989,821 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2022-01-01 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2022-01-01 | $0 |
| Value of total assets at end of year | 2022-01-01 | $441,539,381 |
| Value of total assets at beginning of year | 2022-01-01 | $605,499,189 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2022-01-01 | $989,821 |
| Total interest from all sources | 2022-01-01 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2022-01-01 | $0 |
| Administrative expenses professional fees incurred | 2022-01-01 | $119,851 |
| Were there any nonexempt tranactions with any party-in-interest | 2022-01-01 | No |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2022-01-01 | $3,402 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2022-01-01 | $18 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2022-01-01 | $400,863 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2022-01-01 | $649,647 |
| Value of net income/loss | 2022-01-01 | $-143,970,051 |
| Value of net assets at end of year (total assets less liabilities) | 2022-01-01 | $441,138,518 |
| Value of net assets at beginning of year (total assets less liabilities) | 2022-01-01 | $604,849,542 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2022-01-01 | No |
| Were any leases to which the plan was party in default or uncollectible | 2022-01-01 | No |
| Investment advisory and management fees | 2022-01-01 | $869,970 |
| Value of interest in common/collective trusts at end of year | 2022-01-01 | $441,535,979 |
| Value of interest in common/collective trusts at beginning of year | 2022-01-01 | $605,499,171 |
| Net investment gain or loss from common/collective trusts | 2022-01-01 | $-142,980,370 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2022-01-01 | Yes |
| Did the plan have assets held for investment | 2022-01-01 | Yes |
| Aggregate proceeds on sale of assets | 2022-01-01 | $140 |
| 2021 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2021 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2021-12-31 | $0 |
| Total transfer of assets to this plan | 2021-12-31 | $10,200,034 |
| Total transfer of assets from this plan | 2021-12-31 | $128,680,098 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2021-12-31 | $649,647 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2021-12-31 | $935,358 |
| Total income from all sources (including contributions) | 2021-12-31 | $37,571,521 |
| Total loss/gain on sale of assets | 2021-12-31 | $127 |
| Total of all expenses incurred | 2021-12-31 | $1,762,578 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2021-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2021-12-31 | $0 |
| Value of total assets at end of year | 2021-12-31 | $605,499,189 |
| Value of total assets at beginning of year | 2021-12-31 | $688,456,021 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2021-12-31 | $1,762,578 |
| Total interest from all sources | 2021-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2021-12-31 | $0 |
| Administrative expenses professional fees incurred | 2021-12-31 | $155,271 |
| Were there any nonexempt tranactions with any party-in-interest | 2021-12-31 | No |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2021-12-31 | $18 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2021-12-31 | $91 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2021-12-31 | $649,647 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2021-12-31 | $935,358 |
| Value of net income/loss | 2021-12-31 | $35,808,943 |
| Value of net assets at end of year (total assets less liabilities) | 2021-12-31 | $604,849,542 |
| Value of net assets at beginning of year (total assets less liabilities) | 2021-12-31 | $687,520,663 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2021-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2021-12-31 | No |
| Investment advisory and management fees | 2021-12-31 | $1,607,307 |
| Value of interest in common/collective trusts at end of year | 2021-12-31 | $605,499,171 |
| Value of interest in common/collective trusts at beginning of year | 2021-12-31 | $688,455,930 |
| Net investment gain or loss from common/collective trusts | 2021-12-31 | $37,571,394 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2021-12-31 | Yes |
| Did the plan have assets held for investment | 2021-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2021-12-31 | $127 |
| 2020 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2020 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2020-12-31 | $0 |
| Total transfer of assets to this plan | 2020-12-31 | $11,401,298 |
| Total transfer of assets from this plan | 2020-12-31 | $34,645,452 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2020-12-31 | $935,358 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2020-12-31 | $431,639 |
| Total income from all sources (including contributions) | 2020-12-31 | $104,126,706 |
| Total loss/gain on sale of assets | 2020-12-31 | $1,093 |
| Total of all expenses incurred | 2020-12-31 | $1,930,213 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2020-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2020-12-31 | $0 |
| Value of total assets at end of year | 2020-12-31 | $688,456,021 |
| Value of total assets at beginning of year | 2020-12-31 | $608,999,963 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2020-12-31 | $1,930,213 |
| Total interest from all sources | 2020-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2020-12-31 | $0 |
| Administrative expenses professional fees incurred | 2020-12-31 | $139,003 |
| Were there any nonexempt tranactions with any party-in-interest | 2020-12-31 | No |
| Assets. Other investments not covered elsewhere at beginning of year | 2020-12-31 | $0 |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2020-12-31 | $91 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2020-12-31 | $1,355 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2020-12-31 | $935,358 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2020-12-31 | $431,639 |
| Value of net income/loss | 2020-12-31 | $102,196,493 |
| Value of net assets at end of year (total assets less liabilities) | 2020-12-31 | $687,520,663 |
| Value of net assets at beginning of year (total assets less liabilities) | 2020-12-31 | $608,568,324 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2020-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2020-12-31 | No |
| Investment advisory and management fees | 2020-12-31 | $1,791,210 |
| Value of interest in common/collective trusts at end of year | 2020-12-31 | $688,455,930 |
| Value of interest in common/collective trusts at beginning of year | 2020-12-31 | $608,998,608 |
| Net investment gain or loss from common/collective trusts | 2020-12-31 | $104,125,613 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2020-12-31 | Yes |
| Did the plan have assets held for investment | 2020-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2020-12-31 | $1,093 |
| 2019 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2019 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2019-12-31 | $0 |
| Total transfer of assets to this plan | 2019-12-31 | $10,586,661 |
| Total transfer of assets from this plan | 2019-12-31 | $30,327,168 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2019-12-31 | $431,639 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2019-12-31 | $236,055 |
| Total income from all sources (including contributions) | 2019-12-31 | $109,545,352 |
| Total loss/gain on sale of assets | 2019-12-31 | $19,016 |
| Total of all expenses incurred | 2019-12-31 | $1,585,921 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2019-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2019-12-31 | $0 |
| Value of total assets at end of year | 2019-12-31 | $608,999,963 |
| Value of total assets at beginning of year | 2019-12-31 | $520,585,455 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2019-12-31 | $1,585,921 |
| Total interest from all sources | 2019-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2019-12-31 | $0 |
| Administrative expenses professional fees incurred | 2019-12-31 | $122,225 |
| Were there any nonexempt tranactions with any party-in-interest | 2019-12-31 | No |
| Assets. Other investments not covered elsewhere at end of year | 2019-12-31 | $0 |
| Assets. Other investments not covered elsewhere at beginning of year | 2019-12-31 | $0 |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2019-12-31 | $1,355 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2019-12-31 | $846 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2019-12-31 | $431,639 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2019-12-31 | $236,055 |
| Value of net income/loss | 2019-12-31 | $107,959,431 |
| Value of net assets at end of year (total assets less liabilities) | 2019-12-31 | $608,568,324 |
| Value of net assets at beginning of year (total assets less liabilities) | 2019-12-31 | $520,349,400 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2019-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2019-12-31 | No |
| Investment advisory and management fees | 2019-12-31 | $1,463,696 |
| Value of interest in common/collective trusts at end of year | 2019-12-31 | $608,998,608 |
| Value of interest in common/collective trusts at beginning of year | 2019-12-31 | $520,584,609 |
| Net investment gain or loss from common/collective trusts | 2019-12-31 | $109,526,336 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2019-12-31 | Yes |
| Did the plan have assets held for investment | 2019-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2019-12-31 | $19,016 |
| 2018 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2018 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2018-12-31 | $0 |
| Total transfer of assets to this plan | 2018-12-31 | $9,200,000 |
| Total transfer of assets from this plan | 2018-12-31 | $30,756,540 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2018-12-31 | $236,055 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2018-12-31 | $208,328,425 |
| Total income from all sources (including contributions) | 2018-12-31 | $-38,117,428 |
| Total loss/gain on sale of assets | 2018-12-31 | $6,445 |
| Total of all expenses incurred | 2018-12-31 | $906,314 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2018-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2018-12-31 | $0 |
| Value of total assets at end of year | 2018-12-31 | $520,585,455 |
| Value of total assets at beginning of year | 2018-12-31 | $789,258,107 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2018-12-31 | $906,314 |
| Total interest from all sources | 2018-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2018-12-31 | $0 |
| Administrative expenses professional fees incurred | 2018-12-31 | $123,439 |
| Were there any nonexempt tranactions with any party-in-interest | 2018-12-31 | No |
| Assets. Other investments not covered elsewhere at end of year | 2018-12-31 | $0 |
| Assets. Other investments not covered elsewhere at beginning of year | 2018-12-31 | $208,090,727 |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2018-12-31 | $846 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2018-12-31 | $412 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2018-12-31 | $236,055 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2018-12-31 | $208,328,425 |
| Value of net income/loss | 2018-12-31 | $-39,023,742 |
| Value of net assets at end of year (total assets less liabilities) | 2018-12-31 | $520,349,400 |
| Value of net assets at beginning of year (total assets less liabilities) | 2018-12-31 | $580,929,682 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2018-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2018-12-31 | No |
| Investment advisory and management fees | 2018-12-31 | $782,875 |
| Value of interest in common/collective trusts at end of year | 2018-12-31 | $520,584,609 |
| Value of interest in common/collective trusts at beginning of year | 2018-12-31 | $581,166,968 |
| Net investment gain or loss from common/collective trusts | 2018-12-31 | $-38,123,873 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2018-12-31 | Yes |
| Did the plan have assets held for investment | 2018-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2018-12-31 | $6,445 |
| 2017 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2017 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2017-12-31 | $0 |
| Total transfer of assets to this plan | 2017-12-31 | $9,200,000 |
| Total transfer of assets from this plan | 2017-12-31 | $27,840,734 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2017-12-31 | $208,328,425 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2017-12-31 | $824,482 |
| Total income from all sources (including contributions) | 2017-12-31 | $82,761,534 |
| Total loss/gain on sale of assets | 2017-12-31 | $7,033 |
| Total of all expenses incurred | 2017-12-31 | $1,042,894 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2017-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2017-12-31 | $0 |
| Value of total assets at end of year | 2017-12-31 | $789,258,107 |
| Value of total assets at beginning of year | 2017-12-31 | $518,676,258 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2017-12-31 | $1,042,894 |
| Total interest from all sources | 2017-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2017-12-31 | $0 |
| Administrative expenses professional fees incurred | 2017-12-31 | $117,165 |
| Were there any nonexempt tranactions with any party-in-interest | 2017-12-31 | No |
| Assets. Other investments not covered elsewhere at end of year | 2017-12-31 | $208,090,727 |
| Assets. Other investments not covered elsewhere at beginning of year | 2017-12-31 | $600,000 |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2017-12-31 | $412 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2017-12-31 | $224 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2017-12-31 | $208,328,425 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2017-12-31 | $824,482 |
| Value of net income/loss | 2017-12-31 | $81,718,640 |
| Value of net assets at end of year (total assets less liabilities) | 2017-12-31 | $580,929,682 |
| Value of net assets at beginning of year (total assets less liabilities) | 2017-12-31 | $517,851,776 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2017-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2017-12-31 | No |
| Investment advisory and management fees | 2017-12-31 | $925,729 |
| Value of interest in common/collective trusts at end of year | 2017-12-31 | $581,166,968 |
| Value of interest in common/collective trusts at beginning of year | 2017-12-31 | $518,076,034 |
| Net investment gain or loss from common/collective trusts | 2017-12-31 | $82,754,501 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2017-12-31 | Yes |
| Did the plan have assets held for investment | 2017-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2017-12-31 | $7,033 |
| 2016 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2016 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2016-12-31 | $0 |
| Total transfer of assets to this plan | 2016-12-31 | $12,700,000 |
| Total transfer of assets from this plan | 2016-12-31 | $28,898,394 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2016-12-31 | $824,482 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2016-12-31 | $1,966,964 |
| Total income from all sources (including contributions) | 2016-12-31 | $41,656,298 |
| Total loss/gain on sale of assets | 2016-12-31 | $75 |
| Total of all expenses incurred | 2016-12-31 | $1,025,986 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2016-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2016-12-31 | $0 |
| Value of total assets at end of year | 2016-12-31 | $518,676,258 |
| Value of total assets at beginning of year | 2016-12-31 | $495,386,822 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2016-12-31 | $1,025,986 |
| Total interest from all sources | 2016-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2016-12-31 | $0 |
| Administrative expenses professional fees incurred | 2016-12-31 | $112,386 |
| Were there any nonexempt tranactions with any party-in-interest | 2016-12-31 | No |
| Assets. Other investments not covered elsewhere at end of year | 2016-12-31 | $600,000 |
| Assets. Other investments not covered elsewhere at beginning of year | 2016-12-31 | $1,750,000 |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2016-12-31 | $224 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2016-12-31 | $19 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2016-12-31 | $824,482 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2016-12-31 | $1,966,964 |
| Value of net income/loss | 2016-12-31 | $40,630,312 |
| Value of net assets at end of year (total assets less liabilities) | 2016-12-31 | $517,851,776 |
| Value of net assets at beginning of year (total assets less liabilities) | 2016-12-31 | $493,419,858 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2016-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2016-12-31 | No |
| Investment advisory and management fees | 2016-12-31 | $913,600 |
| Value of interest in common/collective trusts at end of year | 2016-12-31 | $518,076,034 |
| Value of interest in common/collective trusts at beginning of year | 2016-12-31 | $493,636,803 |
| Asset value of US Government securities at beginning of year | 2016-12-31 | $0 |
| Net investment gain or loss from common/collective trusts | 2016-12-31 | $41,656,223 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2016-12-31 | Yes |
| Asset. Corporate debt instrument debt (other) at beginning of year | 2016-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at beginning of year | 2016-12-31 | $0 |
| Did the plan have assets held for investment | 2016-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2016-12-31 | $75 |
| 2015 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2015 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2015-12-31 | $0 |
| Total transfer of assets to this plan | 2015-12-31 | $10,200,000 |
| Total transfer of assets from this plan | 2015-12-31 | $-51,062,614 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2015-12-31 | $1,966,964 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2015-12-31 | $241,732 |
| Expenses. Interest paid | 2015-12-31 | $4,705 |
| Amount of participant contributions which was failed to transmit to the plan within the time period described in 29 CFR 251.3-102 | 2015-12-31 | $4,705 |
| Total income from all sources (including contributions) | 2015-12-31 | $-13,385,630 |
| Total loss/gain on sale of assets | 2015-12-31 | $78,620 |
| Total of all expenses incurred | 2015-12-31 | $1,050,385 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2015-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2015-12-31 | $0 |
| Value of total assets at end of year | 2015-12-31 | $495,386,822 |
| Value of total assets at beginning of year | 2015-12-31 | $548,960,219 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2015-12-31 | $1,045,680 |
| Total interest from all sources | 2015-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2015-12-31 | $0 |
| Administrative expenses professional fees incurred | 2015-12-31 | $120,087 |
| Were there any nonexempt tranactions with any party-in-interest | 2015-12-31 | No |
| Assets. Other investments not covered elsewhere at end of year | 2015-12-31 | $1,750,000 |
| Assets. Other investments not covered elsewhere at beginning of year | 2015-12-31 | $0 |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2015-12-31 | $19 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2015-12-31 | $8 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2015-12-31 | $1,966,964 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2015-12-31 | $241,732 |
| Value of net income/loss | 2015-12-31 | $-14,436,015 |
| Value of net assets at end of year (total assets less liabilities) | 2015-12-31 | $493,419,858 |
| Value of net assets at beginning of year (total assets less liabilities) | 2015-12-31 | $548,718,487 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2015-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2015-12-31 | No |
| Investment advisory and management fees | 2015-12-31 | $925,593 |
| Value of interest in common/collective trusts at end of year | 2015-12-31 | $493,636,803 |
| Value of interest in common/collective trusts at beginning of year | 2015-12-31 | $548,960,211 |
| Asset value of US Government securities at end of year | 2015-12-31 | $0 |
| Asset value of US Government securities at beginning of year | 2015-12-31 | $0 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2015-12-31 | Yes |
| Asset. Corporate debt instrument debt (other) at end of year | 2015-12-31 | $0 |
| Asset. Corporate debt instrument debt (other) at beginning of year | 2015-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at end of year | 2015-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at beginning of year | 2015-12-31 | $0 |
| Did the plan have assets held for investment | 2015-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2015-12-31 | $78,620 |
| 2014 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2014 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2014-12-31 | $0 |
| Total transfer of assets to this plan | 2014-12-31 | $10,200,000 |
| Total transfer of assets from this plan | 2014-12-31 | $23,926,878 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2014-12-31 | $241,732 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2014-12-31 | $189,677 |
| Total income from all sources (including contributions) | 2014-12-31 | $54,375,735 |
| Total loss/gain on sale of assets | 2014-12-31 | $34,875 |
| Total of all expenses incurred | 2014-12-31 | $1,002,737 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2014-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2014-12-31 | $0 |
| Value of total assets at end of year | 2014-12-31 | $548,960,219 |
| Value of total assets at beginning of year | 2014-12-31 | $509,262,044 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2014-12-31 | $1,002,737 |
| Total interest from all sources | 2014-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2014-12-31 | $0 |
| Administrative expenses professional fees incurred | 2014-12-31 | $115,956 |
| Were there any nonexempt tranactions with any party-in-interest | 2014-12-31 | No |
| Assets. Other investments not covered elsewhere at end of year | 2014-12-31 | $0 |
| Assets. Other investments not covered elsewhere at beginning of year | 2014-12-31 | $0 |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2014-12-31 | $8 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2014-12-31 | $10 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2014-12-31 | $241,732 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2014-12-31 | $189,677 |
| Total non interest bearing cash at beginning of year | 2014-12-31 | $0 |
| Value of net income/loss | 2014-12-31 | $53,372,998 |
| Value of net assets at end of year (total assets less liabilities) | 2014-12-31 | $548,718,487 |
| Value of net assets at beginning of year (total assets less liabilities) | 2014-12-31 | $509,072,367 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2014-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2014-12-31 | No |
| Investment advisory and management fees | 2014-12-31 | $886,781 |
| Value of interest in common/collective trusts at end of year | 2014-12-31 | $548,960,211 |
| Value of interest in common/collective trusts at beginning of year | 2014-12-31 | $509,262,034 |
| Asset value of US Government securities at end of year | 2014-12-31 | $0 |
| Asset value of US Government securities at beginning of year | 2014-12-31 | $0 |
| Net investment gain or loss from common/collective trusts | 2014-12-31 | $54,340,860 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2014-12-31 | Yes |
| Asset. Corporate debt instrument debt (other) at end of year | 2014-12-31 | $0 |
| Asset. Corporate debt instrument debt (other) at beginning of year | 2014-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at end of year | 2014-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at beginning of year | 2014-12-31 | $0 |
| Did the plan have assets held for investment | 2014-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2014-12-31 | $34,875 |
| 2013 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2013 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2013-12-31 | $0 |
| Total transfer of assets to this plan | 2013-12-31 | $11,700,000 |
| Total transfer of assets from this plan | 2013-12-31 | $22,798,662 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2013-12-31 | $189,677 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2013-12-31 | $106,750 |
| Total income from all sources (including contributions) | 2013-12-31 | $56,231,240 |
| Total loss/gain on sale of assets | 2013-12-31 | $38,292 |
| Total of all expenses incurred | 2013-12-31 | $619,717 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2013-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2013-12-31 | $0 |
| Value of total assets at end of year | 2013-12-31 | $509,262,044 |
| Value of total assets at beginning of year | 2013-12-31 | $464,666,256 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2013-12-31 | $619,717 |
| Total interest from all sources | 2013-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2013-12-31 | $0 |
| Administrative expenses professional fees incurred | 2013-12-31 | $107,171 |
| Were there any nonexempt tranactions with any party-in-interest | 2013-12-31 | No |
| Assets. Other investments not covered elsewhere at end of year | 2013-12-31 | $0 |
| Assets. Other investments not covered elsewhere at beginning of year | 2013-12-31 | $0 |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2013-12-31 | $10 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2013-12-31 | $77 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2013-12-31 | $189,677 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2013-12-31 | $106,750 |
| Total non interest bearing cash at end of year | 2013-12-31 | $0 |
| Total non interest bearing cash at beginning of year | 2013-12-31 | $0 |
| Value of net income/loss | 2013-12-31 | $55,611,523 |
| Value of net assets at end of year (total assets less liabilities) | 2013-12-31 | $509,072,367 |
| Value of net assets at beginning of year (total assets less liabilities) | 2013-12-31 | $464,559,506 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2013-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2013-12-31 | No |
| Investment advisory and management fees | 2013-12-31 | $512,546 |
| Value of interest in common/collective trusts at end of year | 2013-12-31 | $509,262,034 |
| Value of interest in common/collective trusts at beginning of year | 2013-12-31 | $464,666,179 |
| Asset value of US Government securities at end of year | 2013-12-31 | $0 |
| Asset value of US Government securities at beginning of year | 2013-12-31 | $0 |
| Net investment gain or loss from common/collective trusts | 2013-12-31 | $56,192,948 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2013-12-31 | Yes |
| Asset. Corporate debt instrument debt (other) at end of year | 2013-12-31 | $0 |
| Asset. Corporate debt instrument debt (other) at beginning of year | 2013-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at end of year | 2013-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at beginning of year | 2013-12-31 | $0 |
| Did the plan have assets held for investment | 2013-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2013-12-31 | $38,292 |
| 2012 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2012 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2012-12-31 | $0 |
| Total transfer of assets to this plan | 2012-12-31 | $11,700,000 |
| Total transfer of assets from this plan | 2012-12-31 | $21,071,500 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2012-12-31 | $106,750 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2012-12-31 | $112,518 |
| Total income from all sources (including contributions) | 2012-12-31 | $49,882,940 |
| Total loss/gain on sale of assets | 2012-12-31 | $7,462 |
| Total of all expenses incurred | 2012-12-31 | $526,229 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2012-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2012-12-31 | $0 |
| Value of total assets at end of year | 2012-12-31 | $464,666,256 |
| Value of total assets at beginning of year | 2012-12-31 | $424,686,813 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2012-12-31 | $526,229 |
| Total interest from all sources | 2012-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2012-12-31 | $0 |
| Administrative expenses professional fees incurred | 2012-12-31 | $99,591 |
| Were there any nonexempt tranactions with any party-in-interest | 2012-12-31 | No |
| Assets. Other investments not covered elsewhere at end of year | 2012-12-31 | $0 |
| Assets. Other investments not covered elsewhere at beginning of year | 2012-12-31 | $0 |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2012-12-31 | $77 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2012-12-31 | $4 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2012-12-31 | $106,750 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2012-12-31 | $112,518 |
| Total non interest bearing cash at end of year | 2012-12-31 | $0 |
| Total non interest bearing cash at beginning of year | 2012-12-31 | $0 |
| Value of net income/loss | 2012-12-31 | $49,356,711 |
| Value of net assets at end of year (total assets less liabilities) | 2012-12-31 | $464,559,506 |
| Value of net assets at beginning of year (total assets less liabilities) | 2012-12-31 | $424,574,295 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2012-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2012-12-31 | No |
| Investment advisory and management fees | 2012-12-31 | $426,638 |
| Value of interest in common/collective trusts at end of year | 2012-12-31 | $464,666,179 |
| Value of interest in common/collective trusts at beginning of year | 2012-12-31 | $424,686,809 |
| Asset value of US Government securities at end of year | 2012-12-31 | $0 |
| Asset value of US Government securities at beginning of year | 2012-12-31 | $0 |
| Net investment gain or loss from common/collective trusts | 2012-12-31 | $49,875,478 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2012-12-31 | Yes |
| Asset. Corporate debt instrument debt (other) at end of year | 2012-12-31 | $0 |
| Asset. Corporate debt instrument debt (other) at beginning of year | 2012-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at end of year | 2012-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at beginning of year | 2012-12-31 | $0 |
| Did the plan have assets held for investment | 2012-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2012-12-31 | $7,462 |
| 2011 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2011 401k financial data |
|---|
| Total unrealized appreciation/depreciation of assets | 2011-12-31 | $0 |
| Total transfer of assets to this plan | 2011-12-31 | $11,700,000 |
| Total transfer of assets from this plan | 2011-12-31 | $21,534,118 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2011-12-31 | $112,518 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2011-12-31 | $210,873 |
| Total income from all sources (including contributions) | 2011-12-31 | $14,116,997 |
| Total loss/gain on sale of assets | 2011-12-31 | $33,891 |
| Total of all expenses incurred | 2011-12-31 | $518,160 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2011-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2011-12-31 | $0 |
| Value of total assets at end of year | 2011-12-31 | $424,686,813 |
| Value of total assets at beginning of year | 2011-12-31 | $421,020,449 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2011-12-31 | $518,160 |
| Total interest from all sources | 2011-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2011-12-31 | $0 |
| Administrative expenses professional fees incurred | 2011-12-31 | $89,842 |
| Were there any nonexempt tranactions with any party-in-interest | 2011-12-31 | No |
| Assets. Other investments not covered elsewhere at end of year | 2011-12-31 | $0 |
| Assets. Other investments not covered elsewhere at beginning of year | 2011-12-31 | $0 |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2011-12-31 | $4 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2011-12-31 | $36 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2011-12-31 | $112,518 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2011-12-31 | $210,873 |
| Total non interest bearing cash at end of year | 2011-12-31 | $0 |
| Total non interest bearing cash at beginning of year | 2011-12-31 | $0 |
| Value of net income/loss | 2011-12-31 | $13,598,837 |
| Value of net assets at end of year (total assets less liabilities) | 2011-12-31 | $424,574,295 |
| Value of net assets at beginning of year (total assets less liabilities) | 2011-12-31 | $420,809,576 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2011-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2011-12-31 | No |
| Investment advisory and management fees | 2011-12-31 | $428,318 |
| Value of interest in common/collective trusts at end of year | 2011-12-31 | $424,686,809 |
| Value of interest in common/collective trusts at beginning of year | 2011-12-31 | $421,020,413 |
| Asset value of US Government securities at end of year | 2011-12-31 | $0 |
| Asset value of US Government securities at beginning of year | 2011-12-31 | $0 |
| Net investment gain or loss from common/collective trusts | 2011-12-31 | $14,083,106 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2011-12-31 | Yes |
| Asset. Corporate debt instrument debt (other) at end of year | 2011-12-31 | $0 |
| Asset. Corporate debt instrument debt (other) at beginning of year | 2011-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at end of year | 2011-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at beginning of year | 2011-12-31 | $0 |
| Did the plan have assets held for investment | 2011-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2011-12-31 | $33,898 |
| Aggregate carrying amount (costs) on sale of assets | 2011-12-31 | $7 |
| 2010 : NORTHWESTERN ENERGY MASTER RETIREMENT TRUST 2010 401k financial data |
|---|
| Unrealized appreciation/depreciation of other (non real estate) assets | 2010-12-31 | $1 |
| Total unrealized appreciation/depreciation of assets | 2010-12-31 | $1 |
| Total transfer of assets to this plan | 2010-12-31 | $10,000,000 |
| Total transfer of assets from this plan | 2010-12-31 | $20,540,039 |
| Total liabilities at end of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2010-12-31 | $210,873 |
| Total liabilities at beginning of year (benefit claims payable, operating payabales, acquisition indebtedness and other liabilities) | 2010-12-31 | $63,958 |
| Total income from all sources (including contributions) | 2010-12-31 | $48,828,848 |
| Total loss/gain on sale of assets | 2010-12-31 | $-5,754 |
| Total of all expenses incurred | 2010-12-31 | $437,300 |
| Benefit payments and payments to participlants,beneficiaries,insurance carriers and others | 2010-12-31 | $0 |
| Total contributions o plan (from employers,participants, others, non cash contrinutions) | 2010-12-31 | $0 |
| Value of total assets at end of year | 2010-12-31 | $421,020,449 |
| Value of total assets at beginning of year | 2010-12-31 | $383,022,025 |
| Total of administrative expenses incurred including professional, contract, advisory and management fees | 2010-12-31 | $437,300 |
| Total interest from all sources | 2010-12-31 | $0 |
| Total dividends received (eg from common stock, registered investment company shares) | 2010-12-31 | $0 |
| Administrative expenses professional fees incurred | 2010-12-31 | $83,806 |
| Were there any nonexempt tranactions with any party-in-interest | 2010-12-31 | No |
| Assets. Other investments not covered elsewhere at end of year | 2010-12-31 | $0 |
| Assets. Other investments not covered elsewhere at beginning of year | 2010-12-31 | $0 |
| Value of other receiveables (less allowance for doubtful accounts) at end of year | 2010-12-31 | $36 |
| Value of other receiveables (less allowance for doubtful accounts) at beginning of year | 2010-12-31 | $22 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at end of year | 2010-12-31 | $210,873 |
| Other liabilities (not benefit claims, operating payabales oe acquisition indebtedness) at beginning of year | 2010-12-31 | $63,958 |
| Total non interest bearing cash at end of year | 2010-12-31 | $0 |
| Total non interest bearing cash at beginning of year | 2010-12-31 | $0 |
| Value of net income/loss | 2010-12-31 | $48,391,548 |
| Value of net assets at end of year (total assets less liabilities) | 2010-12-31 | $420,809,576 |
| Value of net assets at beginning of year (total assets less liabilities) | 2010-12-31 | $382,958,067 |
| Were any loans by the plan or fixed income obligations due to the plan in default | 2010-12-31 | No |
| Were any leases to which the plan was party in default or uncollectible | 2010-12-31 | No |
| Investment advisory and management fees | 2010-12-31 | $353,494 |
| Value of interest in common/collective trusts at end of year | 2010-12-31 | $421,020,413 |
| Value of interest in common/collective trusts at beginning of year | 2010-12-31 | $383,022,003 |
| Asset value of US Government securities at end of year | 2010-12-31 | $0 |
| Asset value of US Government securities at beginning of year | 2010-12-31 | $0 |
| Net investment gain or loss from common/collective trusts | 2010-12-31 | $48,834,601 |
| Were any plan transactions or series of transactions in excess of 5% of the current value of the plan assets | 2010-12-31 | Yes |
| Asset. Corporate debt instrument debt (other) at end of year | 2010-12-31 | $0 |
| Asset. Corporate debt instrument debt (other) at beginning of year | 2010-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at end of year | 2010-12-31 | $0 |
| Assets. Corporate common stocks other than exployer securities at beginning of year | 2010-12-31 | $0 |
| Did the plan have assets held for investment | 2010-12-31 | Yes |
| Aggregate proceeds on sale of assets | 2010-12-31 | $141,169 |
| Aggregate carrying amount (costs) on sale of assets | 2010-12-31 | $146,923 |
