Accumulated Other Comprehensive Loss - Reclassification Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense - Borrowed funds	$ 724	$ 991	$ 1,478	$ 1,880
Income tax (expense)	(11)	(101)	(32)	(155)
Net (loss)	(70)	(323)	(170)	(650)
General and administrative	133	183	280	369
Reclassification from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net (loss)	5	11	11	27
Reclassification from AOCI | Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense - Borrowed funds	7	16	16	39
Income tax (expense)	(2)	(4)	(4)	(10)
Net (loss)	5	12	12	29
Reclassification from AOCI | Pension and Post-retirement Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net (loss)	0	(1)	(1)	(2)
Reclassification from AOCI | Amortization of actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax (expense)	(1)	0	(1)	0
General and administrative	$ (1)	$ (1)	$ (2)	$ (2)