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Fair Value Measurements - Fair Value of Assets and Liabilities (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021
ASSETS |  |
Commodity contracts, assets | $ 132,229 |
Commodity contracts, liabilities | (21,163) |
Nuclear decommissioning trust | 1,073,410 | $ 1,294,757
Nuclear decommissioning trust, other | 476,409 | 567,266
Other special use fund | 347,231 | 358,410
Other special use funds, other | 963 | 936
Total assets | 1,552,870 | 1,763,556
Total assets, other | 456,209 | $ 563,512
LIABILITIES |  |
Derivative instruments, other | 15,357 |
Derivative instruments, total | (42,446) |
Total liabilities | (42,446) |
Total liabilities other | $ 15,357 |
DerivativeLiabilityStatementOfFinancialPositionExtensibleEnumerationNotDisclosedFlag | Subtotal risk management activities - derivative instruments | Subtotal risk management activities - derivative instruments
Commodity Contracts |  |
ASSETS |  |
Commodity contracts, assets | $ 153,261 | $ 115,079
LIABILITIES |  |
Derivative instruments | (56,893) | (7,478)
Derivative instruments, total | (41,537) | (4,373)
Commodity contracts |  |
ASSETS |  |
Commodity contracts, assets | 132,098 | 110,389
Commodity contracts, liabilities | (21,163) | (4,690)
LIABILITIES |  |
Derivative instruments, other | 15,357 | 3,105
Derivative instruments, total | (41,537) | (4,373)
Interest rate swaps |  |
ASSETS |  |
Commodity contracts, assets | 131 |
Commodity contracts, liabilities | 0 |
LIABILITIES |  |
Derivative instruments, other | 0 |
Derivative instruments, total | (909) |
Equity securities |  |
ASSETS |  |
Nuclear decommissioning trust | 18,485 | 17,482
Nuclear decommissioning trust, other | 3,827 | (27,782)
Other special use fund | 67,937 | 48,506
Other special use funds, other | 963 | 936
U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trust | 472,582 | 595,048
U.S. Treasury debt |  |
ASSETS |  |
Nuclear decommissioning trust | 211,923 | 240,745
Other special use fund | 275,267 | 298,170
Corporate debt |  |
ASSETS |  |
Nuclear decommissioning trust | 149,226 | 203,454
Mortgage-backed securities |  |
ASSETS |  |
Nuclear decommissioning trust | 147,938 | 155,574
Municipal bonds |  |
ASSETS |  |
Nuclear decommissioning trust | 64,881 | 72,189
Other special use fund | 4,027 | 11,734
Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trust | 8,375 | 10,265
Level 1 |  |
ASSETS |  |
Commodity contracts, assets | 0 |
Nuclear decommissioning trust | 226,581 | 286,009
Other special use fund | 342,241 | 345,740
Total assets | 568,822 | 631,749
LIABILITIES |  |
Derivative instruments | 0 |
Total liabilities | 0 |
Level 1 | Commodity contracts |  |
ASSETS |  |
Commodity contracts, assets | 0 | 0
LIABILITIES |  |
Derivative instruments | 0 | 0
Level 1 | Interest rate swaps |  |
ASSETS |  |
Commodity contracts, assets | 0 |
LIABILITIES |  |
Derivative instruments | 0 |
Level 1 | Equity securities |  |
ASSETS |  |
Nuclear decommissioning trust | 14,658 | 45,264
Other special use fund | 66,974 | 47,570
Level 1 | U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Level 1 | U.S. Treasury debt |  |
ASSETS |  |
Nuclear decommissioning trust | 211,923 | 240,745
Other special use fund | 275,267 | 298,170
Level 1 | Corporate debt |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Level 1 | Mortgage-backed securities |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Level 1 | Municipal bonds |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Other special use fund | 0 | 0
Level 1 | Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Level 2 |  |
ASSETS |  |
Commodity contracts, assets | 127,260 |
Nuclear decommissioning trust | 370,420 | 441,482
Other special use fund | 4,027 | 11,734
Total assets | 501,707 | 568,295
LIABILITIES |  |
Derivative instruments | (26,783) |
Total liabilities | (26,783) |
Level 2 | Commodity contracts |  |
ASSETS |  |
Commodity contracts, assets | 127,129 | 115,079
LIABILITIES |  |
Derivative instruments | (25,874) | (4,740)
Level 2 | Interest rate swaps |  |
ASSETS |  |
Commodity contracts, assets | 131 |
LIABILITIES |  |
Derivative instruments | (909) |
Level 2 | Equity securities |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Other special use fund | 0 | 0
Level 2 | U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Level 2 | U.S. Treasury debt |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Other special use fund | 0 | 0
Level 2 | Corporate debt |  |
ASSETS |  |
Nuclear decommissioning trust | 149,226 | 203,454
Level 2 | Mortgage-backed securities |  |
ASSETS |  |
Nuclear decommissioning trust | 147,938 | 155,574
Level 2 | Municipal bonds |  |
ASSETS |  |
Nuclear decommissioning trust | 64,881 | 72,189
Other special use fund | 4,027 | 11,734
Level 2 | Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trust | 8,375 | 10,265
Level 3 |  |
ASSETS |  |
Commodity contracts, assets | 26,132 |
Nuclear decommissioning trust | 0 | 0
Other special use fund | 0 | 0
Total assets | 26,132 | 0
LIABILITIES |  |
Derivative instruments | (31,020) |
Total liabilities | (31,020) |
Level 3 | Commodity contracts |  |
ASSETS |  |
Commodity contracts, assets | 26,132 | 0
LIABILITIES |  |
Derivative instruments | (31,020) | (2,738)
Level 3 | Interest rate swaps |  |
ASSETS |  |
Commodity contracts, assets | 0 |
LIABILITIES |  |
Derivative instruments | 0 |
Level 3 | Equity securities |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Other special use fund | 0 | 0
Level 3 | U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Level 3 | U.S. Treasury debt |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Other special use fund | 0 | 0
Level 3 | Corporate debt |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Level 3 | Mortgage-backed securities |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Level 3 | Municipal bonds |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Other special use fund | 0 | 0
Level 3 | Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trust | 0 | 0
Level 3 | Forward Contracts | Commodity Contracts |  |
ASSETS |  |
Total assets | 26,132 | 0
LIABILITIES |  |
Total liabilities | (31,020) | (2,738)
Level 3 | Forward Contracts | Natural Gas: | Commodity Contracts | Discounted Cash Flows |  |
ASSETS |  |
Total assets | 0 | 0
LIABILITIES |  |
Total liabilities | (29,261) | (2,738)
NAV | U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trust | $ 472,582 | $ 595,048

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