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Fair Value Measurements - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands | Jun. 30, 2024 | Dec. 31, 2023
--- | --- | ---
ASSETS |  |
Cash equivalents | $ 16 | $ 10
Nuclear decommissioning trust: | 1,245,593 | 1,201,246
Nuclear decommissioning trust, other | 392,452 | 408,849
Other special use funds | 367,804 | 362,781
Other special use funds, other | 2,287 | 2,196
Total assets | 1,614,173 | 1,570,845
Total assets, other | 392,054 | 409,356
Commodity contracts |  |
ASSETS |  |
Commodity contracts, assets | 760 | 6,808
Commodity contracts assets, other | (2,685) | (1,689)
LIABILITIES |  |
Gross derivative liability, other | (5,081) | 4,823
Interest rate swaps | (130,673) | (123,888)
Equity securities |  |
ASSETS |  |
Nuclear decommissioning trust: | 18,241 | 10,297
Nuclear decommissioning trust, other | 1,444 | (767)
Other special use funds | 49,076 | 43,187
Other special use funds, other | 2,287 | 2,196
U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trust: | 391,008 | 409,616
U.S. Treasury debt |  |
ASSETS |  |
Nuclear decommissioning trust: | 323,847 | 319,734
Other special use funds | 318,728 | 319,594
Corporate debt |  |
ASSETS |  |
Nuclear decommissioning trust: | 219,337 | 188,317
Mortgage-backed securities |  |
ASSETS |  |
Nuclear decommissioning trust: | 215,154 | 208,306
Municipal bonds |  |
ASSETS |  |
Nuclear decommissioning trust: | 48,332 | 59,323
Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trust: | 29,674 | 5,653
Level 1 |  |
ASSETS |  |
Cash equivalents | 16 | 10
Nuclear decommissioning trust: | 340,644 | 330,798
Other special use funds | 365,517 | 360,585
Total assets | 706,177 | 691,393
Level 1 | Commodity contracts |  |
ASSETS |  |
Commodity contracts, assets | 0 | 0
LIABILITIES |  |
Gross derivative liability | 0 | 0
Level 1 | Equity securities |  |
ASSETS |  |
Nuclear decommissioning trust: | 16,797 | 11,064
Other special use funds | 46,789 | 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: | 323,847 | 319,734
Other special use funds | 318,728 | 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
Level 1 | Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trust: | 0 | 0
Level 2 |  |
ASSETS |  |
Cash equivalents | 0 | 0
Nuclear decommissioning trust: | 512,497 | 461,599
Other special use funds | 0 | 0
Total assets | 515,704 | 463,480
Level 2 | Commodity contracts |  |
ASSETS |  |
Commodity contracts, assets | 3,207 | 1,881
LIABILITIES |  |
Gross derivative liability | (103,714) | (127,016)
Level 2 | Equity securities |  |
ASSETS |  |
Nuclear decommissioning trust: | 0 | 0
Other special use funds | 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 funds | 0 | 0
Level 2 | Corporate debt |  |
ASSETS |  |
Nuclear decommissioning trust: | 219,337 | 188,317
Level 2 | Mortgage-backed securities |  |
ASSETS |  |
Nuclear decommissioning trust: | 215,154 | 208,306
Level 2 | Municipal bonds |  |
ASSETS |  |
Nuclear decommissioning trust: | 48,332 | 59,323
Level 2 | Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trust: | 29,674 | 5,653
Level 3 |  |
ASSETS |  |
Cash equivalents | 0 | 0
Nuclear decommissioning trust: | 0 | 0
Other special use funds | 0 | 0
Total assets | 238 | 6,616
Level 3 | Commodity contracts |  |
ASSETS |  |
Commodity contracts, assets | 238 | 6,616
LIABILITIES |  |
Gross derivative liability | (21,878) | (1,695)
Level 3 | Equity securities |  |
ASSETS |  |
Nuclear decommissioning trust: | 0 | 0
Other special use funds | 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 funds | 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
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: | $ 391,008 | $ 409,616

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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
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