Accumulated Other Comprehensive Income - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Unrealized Gains (Losses) on Investment Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax on net unrealized gains (losses) arising during period	$ (195)	$ 245
Tax on reclassification adjustment	(7)	(7)
Tax on reversal of provision for credit losses realized in net income (loss)	0	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 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax on net unrealized gains (losses) arising during period	(3)	128
Unrealized Gains (Losses) on Derivatives Designated as Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax on net unrealized gains (losses) arising during period	(4)	28
Tax on reclassification adjustment	$ 1	$ 1
Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member] | Unrealized Gains (Losses) on Investment Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax on cumulative effect adjustment			$ 1