Stockholders' Equity and EPS - Reclassification of AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Gains on investment securities, net	$ (761)	$ (421)	$ (135)
Income tax expense	651	448	425
Net interest income	(3,179)	(2,157)	(2,097)
Total reclassification adjustment for (gains) losses included in net income, net of tax	(1,770)	(1,191)	(1,137)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total reclassification adjustment for (gains) losses included in net income, net of tax	(68)	(80)	6
Accumulated Net Unrealized Investment Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Gains on investment securities, net	(31)	(61)	4
Income tax expense	9	17	(1)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income tax expense	17	14	(2)
Net interest income	$ (63)	$ (50)	$ 5