Stockholders' Equity - Reclassifications from AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	$ 5,822	$ 6,025
Interest expense	439	1,084
Non-interest income	118	145
Income from continuing operations before income taxes	4,196	(1,903)
Income tax provision	869	(563)
Net Income (Loss)	3,325	(1,340)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income (Loss)	247	321
Accumulated Net Unrealized Investment Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income [Member] | Available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-interest income	4	0
Income tax provision	1	0
Net Income (Loss)	3	0
Hedging Relationships | Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest rate contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	235	26
Hedging Relationships | Reclassification out of Accumulated Other Comprehensive Income [Member] | Foreign exchange contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	1	7
Interest expense	(1)	(1)
Non-interest income	85	392
Income from continuing operations before income taxes	320	424
Income tax provision	77	103
Net Income (Loss)	243	321
Other | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations before income taxes	1	0
Income tax provision	0	0
Net Income (Loss)	$ 1	$ 0