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Fair Value Measurements - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2022 | Dec. 31, 2023
Fair Value Disclosures [Abstract] |  |
Derivative liability statement of financial position not disclosed flag | interest rate derivative instruments |
ASSETS |  |
Cash equivalents |  | $ 10
Commodity contracts, assets | $ 132,229 |
Commodity contracts assets, other | (21,163) |
Nuclear decommissioning trust | 1,073,410 | 1,201,246
Nuclear decommissioning trust, other | 476,409 | 408,849
Other special use fund | 347,231 | 362,781
Other special use funds, other | 963 | 2,196
Total assets | 1,552,870 | 1,570,845
Total assets, other | 456,209 | 409,356
LIABILITIES |  |
Derivative instruments, other | 15,357 |
Derivative instruments, total | (42,446) |
Total liabilities | (42,446) |
Total liabilities, other | 15,357 |
Commodity contracts |  |
ASSETS |  |
Commodity contracts, assets | 132,098 | 6,808
Commodity contracts assets, other | (21,163) | (1,689)
LIABILITIES |  |
Derivative instruments, other | 15,357 | 4,823
Derivative instruments, total | (41,537) | (123,888)
Interest rate swaps |  |
ASSETS |  |
Commodity contracts, assets | 131 |
Commodity contracts assets, other | 0 |
LIABILITIES |  |
Derivative instruments, other | 0 |
Derivative instruments, total | (909) |
Equity securities |  |
ASSETS |  |
Nuclear decommissioning trust | 18,485 | 10,297
Nuclear decommissioning trust, other | 3,827 | (767)
Other special use fund | 67,937 | 43,187
Other special use funds, other | 963 | 2,196
U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trust | 472,582 | 409,616
U.S. Treasury debt |  |
ASSETS |  |
Nuclear decommissioning trust | 211,923 | 319,734
Other special use fund | 275,267 | 319,594
Corporate debt |  |
ASSETS |  |
Nuclear decommissioning trust | 149,226 | 188,317
Mortgage-backed securities |  |
ASSETS |  |
Nuclear decommissioning trust | 147,938 | 208,306
Municipal bonds |  |
ASSETS |  |
Nuclear decommissioning trust | 64,881 | 59,323
Other special use fund | 4,027 | 0
Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trust | 8,375 | 5,653
Level 1 |  |
ASSETS |  |
Cash equivalents |  | 10
Commodity contracts, assets | 0 |
Nuclear decommissioning trust | 226,581 | 330,798
Other special use fund | 342,241 | 360,585
Total assets | 568,822 | 691,393
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 | 11,064
Other special use fund | 66,974 | 40,991
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 | 319,734
Other special use fund | 275,267 | 319,594
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 |  |
Cash equivalents |  | 0
Commodity contracts, assets | 127,260 |
Nuclear decommissioning trust | 370,420 | 461,599
Other special use fund | 4,027 | 0
Total assets | 501,707 | 463,480
LIABILITIES |  |
Derivative instruments | (26,783) |
Total liabilities | (26,783) |
Level 2 | Commodity contracts |  |
ASSETS |  |
Commodity contracts, assets | 127,129 | 1,881
LIABILITIES |  |
Derivative instruments | (25,874) | (127,016)
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 | 188,317
Level 2 | Mortgage-backed securities |  |
ASSETS |  |
Nuclear decommissioning trust | 147,938 | 208,306
Level 2 | Municipal bonds |  |
ASSETS |  |
Nuclear decommissioning trust | 64,881 | 59,323
Other special use fund | 4,027 | 0
Level 2 | Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trust | 8,375 | 5,653
Level 3 |  |
ASSETS |  |
Cash equivalents |  | 0
Commodity contracts, assets | 26,132 |
Nuclear decommissioning trust | 0 | 0
Other special use fund | 0 | 0
Total assets | 26,132 | 6,616
LIABILITIES |  |
Derivative instruments | (31,020) |
Total liabilities | (31,020) |
Level 3 | Commodity contracts |  |
ASSETS |  |
Commodity contracts, assets | 26,132 | 6,616
LIABILITIES |  |
Derivative instruments | (31,020) | (1,695)
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
Fair Value Measured at Net Asset Value Per Share | U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trust | $ 472,582 | $ 409,616

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