Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	$ 11,374
Total other comprehensive income (loss)	(108)	$ 365
Balance at end of period, common equity	11,491	12,426
Accumulated other comprehensive loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	(1,926)	(2,575)
Total other comprehensive income (loss)	(108)	365
Balance at end of period, common equity	(2,034)	(2,210)
Unrealized gains (losses) on investment securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	(1,734)	(2,270)
Net unrealized gains (losses) arising during the period, net of tax	(106)	207
Reclassification adjustment for (gains) losses realized in net income (loss), net of tax	(2)	(2)
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	(1)
Total other comprehensive income (loss)	(107)	204
Balance at end of period, common equity	(1,841)	(2,066)
Tax on net unrealized gains (losses) arising during period	(36)	68
Tax on reclassification adjustment (less than)	(1)	(1)
Tax on amortization of net unrealized losses on securities transferred from available-for-sale to held-to-maturity realized in net income (loss)	1	(1)
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	61	86
Net unrealized gains (losses) arising during the period, net of tax	(37)	63
Total other comprehensive income (loss)	(37)	63
Balance at end of period, common equity	24	149
Tax on net unrealized gains (losses) arising during period	(12)	21
Unrealized gains (losses) on derivatives designated as cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	(260)	(396)
Net unrealized gains (losses) arising during the period, net of tax	31	64
Reclassification adjustment for (gains) losses realized in net income (loss), net of tax	5	34
Total other comprehensive income (loss)	36	98
Balance at end of period, common equity	(224)	(298)
Tax on net unrealized gains (losses) arising during period	10	21
Tax on reclassification adjustment (less than)	2	11
Pension and postretirement benefit liability
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	7	5
Balance at end of period, common equity	$ 7	$ 5