Stockholders' Equity and EPS - Reclassification out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains/(loss) on investment securities, net	$ (157)	$ 305	$ (72)	$ 472
Related tax benefit	(132)	(173)	(314)	(360)
Net interest income	1,167	728	2,249	1,388
Total reclassification adjustment for gains included in net income, net of tax	333	502	805	1,034
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	(9)	(11)	(55)	(22)
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/(loss) on investment securities, net	1	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)	(5)	8	9
Net interest income	$ (14)	$ (16)	$ (29)	$ (31)