Accumulated Other Comprehensive Income (Loss) - (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	$ 15,775
Total other comprehensive loss	(1,166)	$ (653)
Balance at end of period, common equity	14,808	16,709
Accumulated other comprehensive income (loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	(179)	679
Total other comprehensive loss	(1,166)	(653)
Balance at end of period, common equity	(1,345)	26
Unrealized gains (losses) on investment securities:
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	(65)	750
Net unrealized gains (losses) arising during the period, net of tax	(1,029)	(613)
Reclassification adjustment for (gains) losses realized in net income (loss)	(15)	(22)
Reversal of provision for credit losses realized in net income (loss), net of tax	(1)	0
Amortization of net unrealized losses on securities transferred from available-for-sale to held-to-maturity realized in net income (loss), net of tax	2	4
Total other comprehensive loss	(1,043)	(631)
Balance at end of period, common equity	(1,108)	119
Tax on net unrealized gains (losses) arising during period	(327)	(195)
Tax on reclassification adjustment	(5)	(7)
Tax on reversal of provision for credit losses realized in net income (loss)	(1)	0
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	27	15
Net unrealized gains (losses) arising during the period, net of tax	29	(10)
Total other comprehensive loss	29	(10)
Balance at end of period, common equity	56	5
Tax on net unrealized gains (losses) arising during period	9	(3)
Unrealized gains (losses) on derivatives designated as cash flow hedges:
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	(138)	(79)
Net unrealized gains (losses) arising during the period, net of tax	(153)	(13)
Reclassification adjustment for (gains) losses realized in net income (loss)	1	1
Total other comprehensive loss	(152)	(12)
Balance at end of period, common equity	(290)	(91)
Tax on net unrealized gains (losses) arising during period	(48)	(4)
Tax on reclassification adjustment	1	1
Pension and postretirement benefit liability:
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period, common equity	(3)	(7)
Balance at end of period, common equity	$ (3)	$ (7)