Fair Value - Summary of Recurring Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Assets
Cash equivalents	$ 8	$ 9
Equity securities, Fair Value	1,132	1,013
Debt securities	593	579
Receivables (payables), net	4	(26)
NDT funds	1,737	1,575
Derivative assets, netting	(139)	(200)
Total assets	1,809	1,670
Liabilities
Derivative liabilities, netting	(162)	(257)
Total liabilities	10	43
Commodity derivatives
Assets
Derivative assets, netting	(139)	(200)
Derivative assets, total	72	94
Liabilities
Derivative liabilities, netting	(162)	(257)
Derivative liabilities, total	7	37
Interest rate derivatives
Assets
Derivative assets, total	0	1
Liabilities
Derivative liabilities, total	3	6
U.S. Government debt securities
Assets
Debt securities	328	337
Municipal debt securities
Assets
Debt securities	88	86
Corporate debt securities
Assets
Debt securities	177	156
Level 1
Assets
Cash equivalents	0	0
Equity securities, Fair Value	755	629
NDT funds	1,083	966
Total assets	1,191	1,064
Liabilities
Total liabilities	131	155
Level 1 | Commodity derivatives
Assets
Derivative assets	108	98
Liabilities
Derivative liabilities	131	155
Level 1 | Interest rate derivatives
Assets
Derivative assets, total	0	0
Liabilities
Derivative liabilities	0	0
Level 1 | U.S. Government debt securities
Assets
Debt securities	328	337
Level 1 | Municipal debt securities
Assets
Debt securities	0	0
Level 1 | Corporate debt securities
Assets
Debt securities	0	0
Level 2
Assets
Cash equivalents	0	0
Equity securities, Fair Value	0	0
NDT funds	265	242
Total assets	368	439
Liabilities
Total liabilities	41	145
Level 2 | Commodity derivatives
Assets
Derivative assets	103	196
Liabilities
Derivative liabilities	38	139
Level 2 | Interest rate derivatives
Assets
Derivative assets, total	0	1
Liabilities
Derivative liabilities	3	6
Level 2 | U.S. Government debt securities
Assets
Debt securities	0	0
Level 2 | Municipal debt securities
Assets
Debt securities	88	86
Level 2 | Corporate debt securities
Assets
Debt securities	177	156
NAV
Assets
Cash equivalents	8	9
Equity securities, Fair Value	377	384
NDT funds	385	393
Total assets	385	393
Liabilities
Total liabilities	0	0
NAV | Commodity derivatives
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
NAV | Interest rate derivatives
Assets
Derivative assets, total	0	0
Liabilities
Derivative liabilities	0	0
NAV | U.S. Government debt securities
Assets
Debt securities	0	0
NAV | Municipal debt securities
Assets
Debt securities	0	0
NAV | Corporate debt securities
Assets
Debt securities	$ 0	$ 0