Related Party Transactions - PAC (Details) - USD ($) $ in Millions		12 Months Ended
	Dec. 17, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Accounts payable		$ 2,928	$ 3,175
Revenues		25,920	25,602	$ 26,337
PAC
Related Party Transaction [Line Items]
Accounts payable		1,462	1,560
Revenues		6,600	5,936	5,679
Other receivables		245	447
Income tax receivable (payable), related parties current			114
Related party, cash received (paid) income taxes		$ 349	292	185
PAC | Preferred Stock Class, Serial Preferred, 6.00%
Related Party Transaction [Line Items]
Preferred stock, dividend rate	6.00%	6.00%
PAC | Preferred Stock Class, Serial Preferred, 7.00%
Related Party Transaction [Line Items]
Preferred stock, dividend rate	7.00%	7.00%
PAC | Federal
Related Party Transaction [Line Items]
Income tax receivable (payable), related parties current		$ 3
PAC | State
Related Party Transaction [Line Items]
Income tax receivable (payable), related parties current		(11)
PAC | Intercompany administrative services agreement and a mutual assistance agreement
Related Party Transaction [Line Items]
Related party amounts of transaction		147	168	123
PAC | Business services
Related Party Transaction [Line Items]
Purchases from related party		8	6	8
PAC | Transportation costs
Related Party Transaction [Line Items]
Purchases from related party		22	24	21
PAC | Long-term master materials supply contract
Related Party Transaction [Line Items]
Purchases from related party		5	17	8
PAC | Coal purchases
Related Party Transaction [Line Items]
Purchases from related party		132	139	119
PAC | Related party | Intercompany administrative services agreement and a mutual assistance agreement
Related Party Transaction [Line Items]
Accounts payable		89	15
Revenues		41	44	$ 23
Other receivables		5	8
PAC | Related party | PPW Holdings LLC invoices
Related Party Transaction [Line Items]
Other receivables		20
PAC | Equity method investee | Coal purchases
Related Party Transaction [Line Items]
Accounts payable		$ 36	$ 34