Investment Securities - Summary of Remaining Contractual Principal Maturities for Held-to-Maturity Securities (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	$ 91,667	$ 97,227
U.S. agency debentures
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	512	615
Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	59,080	63,676
Residential mortgage-backed securities | Agency-issued collateralized mortgage obligations—fixed rate
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	10,431	10,090
Residential mortgage-backed securities | Agency-issued collateralized mortgage obligations—variable rate
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	93	101
Agency-issued commercial mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	14,118	14,721
Municipal bonds and notes
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	6,776	7,315
After One Year to Five Years, Amortized Cost	187
After Five Years to Ten Years, Amortized Cost	1,231
Corporate bonds
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	657	$ 709
After One Year to Five Years, Amortized Cost	52
After Five Years to Ten Years, Amortized Cost	654
Held-to-maturity Securities
Schedule of Held-to-maturity Securities [Line Items]
Net Carry Value	98,707
Fair Value	91,667
One Year or Less, Amortized Cost	73
One Year or Less, Fair Value	73
After One Year to Five Years, Amortized Cost	563
After One Year to Five Years, Fair Value	548
After Five Years to Ten Years, Amortized Cost	4,725
After Five Years to Ten Years, Fair Value	4,524
After Ten Years, Amortized Cost	93,346
After Ten Years, Fair Value	$ 86,522
Held-to-maturity Securities | Lower Limit
Schedule of Held-to-maturity Securities [Line Items]
Mortgage-backed securities contractual maturities (in years)	10 years
Held-to-maturity Securities | Upper Limit
Schedule of Held-to-maturity Securities [Line Items]
Mortgage-backed securities contractual maturities (in years)	30 years
Held-to-maturity Securities | U.S. agency debentures
Schedule of Held-to-maturity Securities [Line Items]
Net Carry Value	$ 536
Fair Value	512
One Year or Less, Amortized Cost	4
One Year or Less, Fair Value	4
After One Year to Five Years, Amortized Cost	109
After One Year to Five Years, Fair Value	106
After Five Years to Ten Years, Amortized Cost	423
After Five Years to Ten Years, Fair Value	402
After Ten Years, Amortized Cost	0
After Ten Years, Fair Value	0
Held-to-maturity Securities | Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Net Carry Value	63,517
Fair Value	59,080
One Year or Less, Amortized Cost	0
One Year or Less, Fair Value	0
After One Year to Five Years, Amortized Cost	6
After One Year to Five Years, Fair Value	6
After Five Years to Ten Years, Amortized Cost	1,181
After Five Years to Ten Years, Fair Value	1,161
After Ten Years, Amortized Cost	62,330
After Ten Years, Fair Value	57,913
Held-to-maturity Securities | Residential mortgage-backed securities | Agency-issued collateralized mortgage obligations—fixed rate
Schedule of Held-to-maturity Securities [Line Items]
Net Carry Value	11,231
Fair Value	10,431
One Year or Less, Amortized Cost	0
One Year or Less, Fair Value	0
After One Year to Five Years, Amortized Cost	31
After One Year to Five Years, Fair Value	31
After Five Years to Ten Years, Amortized Cost	266
After Five Years to Ten Years, Fair Value	259
After Ten Years, Amortized Cost	10,934
After Ten Years, Fair Value	10,141
Held-to-maturity Securities | Residential mortgage-backed securities | Agency-issued collateralized mortgage obligations—variable rate
Schedule of Held-to-maturity Securities [Line Items]
Net Carry Value	93
Fair Value	93
One Year or Less, Amortized Cost	0
One Year or Less, Fair Value	0
After One Year to Five Years, Amortized Cost	0
After One Year to Five Years, Fair Value	0
After Five Years to Ten Years, Amortized Cost	0
After Five Years to Ten Years, Fair Value	0
After Ten Years, Amortized Cost	93
After Ten Years, Fair Value	93
Held-to-maturity Securities | Agency-issued commercial mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Net Carry Value	15,141
Fair Value	14,118
One Year or Less, Amortized Cost	32
One Year or Less, Fair Value	32
After One Year to Five Years, Amortized Cost	178
After One Year to Five Years, Fair Value	170
After Five Years to Ten Years, Amortized Cost	970
After Five Years to Ten Years, Fair Value	904
After Ten Years, Amortized Cost	13,961
After Ten Years, Fair Value	13,012
Held-to-maturity Securities | Municipal bonds and notes
Schedule of Held-to-maturity Securities [Line Items]
Net Carry Value	7,483
Fair Value	6,776
One Year or Less, Amortized Cost	37
One Year or Less, Fair Value	37
After One Year to Five Years, Fair Value	186
After Five Years to Ten Years, Fair Value	1,190
After Ten Years, Amortized Cost	6,028
After Ten Years, Fair Value	5,363
Held-to-maturity Securities | Corporate bonds
Schedule of Held-to-maturity Securities [Line Items]
Net Carry Value	706
Fair Value	657
One Year or Less, Amortized Cost	0
One Year or Less, Fair Value	0
After One Year to Five Years, Fair Value	49
After Five Years to Ten Years, Fair Value	608
After Ten Years, Amortized Cost	0
After Ten Years, Fair Value	$ 0