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Investment Securities - Components of Held-to-Maturity Investment Securities (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 98,713	$ 98,202
Unrealized Gains	48	368
Unrealized Losses	(7,094)	(1,343)
Fair Value	91,667	97,227
Allowance for Credit Losses	6	7	$ 1	$ 1
U.S. agency debentures
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	536	609
Unrealized Gains	0	8
Unrealized Losses	(24)	(2)
Fair Value	512	615
Allowance for Credit Losses	0	0
Residential mortgage-backed securities \| Agency-issued mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	63,517	64,439
Unrealized Gains	7	124
Unrealized Losses	(4,444)	(887)
Fair Value	59,080	63,676
Allowance for Credit Losses	0	0
Residential mortgage-backed securities \| Agency-issued collateralized mortgage obligations—fixed rate
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	11,231	10,226
Unrealized Gains	0	9
Unrealized Losses	(800)	(145)
Fair Value	10,431	10,090
Allowance for Credit Losses	0	0
Residential mortgage-backed securities \| Agency-issued collateralized mortgage obligations—variable rate
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	93	100
Unrealized Gains	0	1
Unrealized Losses	0	0
Fair Value	93	101
Allowance for Credit Losses	0	0
Agency-issued commercial mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	15,141	14,959
Unrealized Gains	7	39
Unrealized Losses	(1,030)	(277)
Fair Value	14,118	14,721
Allowance for Credit Losses	0	0
Municipal bonds and notes
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	7,484	7,157
Unrealized Gains	34	185
Unrealized Losses	(742)	(27)
Fair Value	6,776	7,315
Allowance for Credit Losses	1	1
Corporate bonds
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	711	712
Unrealized Gains	0	2
Unrealized Losses	(54)	(5)
Fair Value	657	709
Allowance for Credit Losses	$ 5	$ 6