Accumulated Other Comprehensive Loss - Reclassification Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense - Borrowed funds	$ 754	$ 889
Income tax (expense)	(21)	(54)
Net income (loss)	(100)	(327)
General and administrative	147	186
Reclassification from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income (loss)	6	16
Reclassification from AOCI | Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense - Borrowed funds	9	23
Income tax (expense)	(2)	(6)
Net income (loss)	7	17
Reclassification from AOCI | Pension and Post-retirement Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income (loss)	(1)	(1)
Reclassification from AOCI | Amortization of actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax (expense)	0	0
General and administrative	$ (1)	$ (1)