Stockholders' Equity and EPS - Reclassification out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains (losses) on investment securities, net	$ (127)	$ 189	$ (199)	$ 661
Related tax benefit	(175)	(149)	(489)	(509)
Net interest income	1,198	852	3,447	2,240
Total reclassification adjustment for gains included in net income, net of tax	429	365	1,234	1,399
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassification adjustment for gains included in net income, net of tax	(10)	(12)	(65)	(34)
Accumulated Net Investment Gain (Loss) Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains (losses) on investment securities, net	0	0	(48)	0
Related tax benefit	0	0	14	0
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Related tax benefit	4	4	12	13
Net interest income	$ (14)	$ (16)	$ (43)	$ (47)