Accumulated Other Comprehensive Loss (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity			$ 11,374,000,000
Total other comprehensive income (loss)	$ 446,000,000	$ (295,000,000)	279,000,000	$ (106,000,000)
Balance at end of period, common equity	12,121,000,000	11,285,000,000	12,121,000,000	11,285,000,000
Accumulated other comprehensive loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	(2,093,000,000)	(2,386,000,000)	(1,926,000,000)	(2,575,000,000)
Total other comprehensive income (loss)	446,000,000	(295,000,000)	279,000,000	(106,000,000)
Balance at end of period, common equity	(1,647,000,000)	(2,681,000,000)	(1,647,000,000)	(2,681,000,000)
Unrealized gains (losses) on investment securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	(1,924,000,000)	(2,129,000,000)	(1,734,000,000)	(2,270,000,000)
Net unrealized gains (losses) arising during the period, net of tax	438,000,000	(346,000,000)	255,000,000	(203,000,000)
Reclassification adjustment for (gains) losses realized in net income (loss), net of tax	112,000,000	0	104,000,000	(2,000,000)
Amortization of net unrealized (gains) losses on securities transferred from available-for-sale to held-to-maturity realized in net income, net of tax			1,000,000	0
Total other comprehensive income (loss)	550,000,000	(346,000,000)	360,000,000	(205,000,000)
Balance at end of period, common equity	(1,374,000,000)	(2,475,000,000)	(1,374,000,000)	(2,475,000,000)
Tax on net unrealized gains (losses) arising during period	145,000,000	(113,000,000)	85,000,000	(66,000,000)
Tax on reclassification adjustment (less than)	36,000,000	0	34,000,000	(1,000,000)
Tax on amortization of net unrealized losses on securities transferred from available-for-sale to held-to-maturity realized in net income (loss)			1,000,000	0
Unrealized gains (losses) on fair value option liabilities attributable to our own credit spread
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	20,000,000	85,000,000	61,000,000	86,000,000
Net unrealized gains (losses) arising during the period, net of tax	4,000,000	(8,000,000)	(37,000,000)	(9,000,000)
Total other comprehensive income (loss)	4,000,000	(8,000,000)	(37,000,000)	(9,000,000)
Balance at end of period, common equity	24,000,000	77,000,000	24,000,000	77,000,000
Tax on net unrealized gains (losses) arising during period	1,000,000	(2,000,000)	(12,000,000)	(3,000,000)
Unrealized gains (losses) on derivatives designated as cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	(196,000,000)	(347,000,000)	(260,000,000)	(396,000,000)
Net unrealized gains (losses) arising during the period, net of tax	(124,000,000)	20,000,000	(77,000,000)	(7,000,000)
Reclassification adjustment for (gains) losses realized in net income (loss), net of tax	17,000,000	40,000,000	34,000,000	116,000,000
Total other comprehensive income (loss)	(107,000,000)	60,000,000	(43,000,000)	109,000,000
Balance at end of period, common equity	(303,000,000)	(287,000,000)	(303,000,000)	(287,000,000)
Tax on net unrealized gains (losses) arising during period	(40,000,000)	7,000,000	(25,000,000)	(1,000,000)
Tax on reclassification adjustment (less than)	5,000,000	13,000,000	11,000,000	37,000,000
Pension and postretirement benefit liability
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	7,000,000	5,000,000	7,000,000	5,000,000
Net unrealized gains (losses) arising during the period, net of tax	(1,000,000)	(1,000,000)	(1,000,000)	(1,000,000)
Total other comprehensive income (loss)	(1,000,000)	(1,000,000)	(1,000,000)	(1,000,000)
Balance at end of period, common equity	6,000,000	4,000,000	6,000,000	4,000,000
Tax on net unrealized gains (losses) arising during period	$ (1,000,000)	$ (1,000,000)	$ (1,000,000)	$ (1,000,000)