Accounting for Derivative Instruments and Hedging Activities - Schedule of Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Derivative [Line Items]
Derivative assets, gross	$ 156	$ 175
Derivative liabilities, gross	(360)	(371)
Fair value of gross derivative assets/(liabilities), net	(204)	(196)
Derivative instruments	0	0
Net amount	(204)	(196)
Energy-related commodity contracts
Derivative [Line Items]
Derivative assets, gross	14	9
Derivative instruments, assets	0	0
Net amount	14	9
Derivative liabilities, gross	(333)	(371)
Derivative instruments, liabilities	0	0
Derivative Liabilities, Net Amount	(333)	(371)
Fair value of gross derivative assets/(liabilities), net	(319)	(362)
Derivative instruments	0	0
Net amount	(319)	(362)
Interest rate contracts
Derivative [Line Items]
Derivative assets, gross	142	166
Derivative instruments, assets	0	0
Net amount	142	166
Derivative liabilities, gross	(27)
Derivative instruments, liabilities	0
Derivative Liabilities, Net Amount	(27)
Fair value of gross derivative assets/(liabilities), net	115	166
Derivative instruments	0	0
Net amount	$ 115	$ 166