Stockholders' Equity - Reclassifications from AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	$ 5,743	$ 5,460	$ 11,565	$ 11,485
Interest expense	396	858	835	1,942
Non-interest income	231	166	349	311
Income (loss) from continuing operations before income taxes	4,568	(1,460)	8,764	(3,363)
Income tax provision	1,031	(543)	1,900	(1,106)
Net income (loss)	3,536	(918)	6,861	(2,258)
Accumulated other comprehensive income	1,792		1,792			$ 3,494
Other comprehensive income (loss), net of tax	9	302	(1,702)	2,833
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	244	(117)	491	204
Securities available for sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income	1,089	2,373	1,089	2,373	$ 1,038	2,186	$ 2,151	$ 935
Other comprehensive income (loss) before reclassifications	51	222	(1,094)	1,446
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	(3)	0
Other comprehensive income (loss), net of tax	51	222	(1,097)	1,446
Securities available for sale | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-interest income	0	0	4	0
Income tax provision	0	0	1	0
Net income (loss)	0	0	3	0
Hedging Relationships
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income	730	1,785	730	1,785	781	1,362	1,728	354
Other comprehensive income (loss) before reclassifications	193	(60)	(145)	1,635
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(244)	117	(487)	(204)
Other comprehensive income (loss), net of tax	(51)	57	(632)	1,431
Hedging Relationships | Interest rate contracts | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	245	142	480	168
Hedging Relationships | Foreign exchange contracts | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	0	2	1	9
Interest expense	(1)	(1)	(2)	(2)
Non-interest income	77	(299)	162	93
Income (loss) from continuing operations before income taxes	321	(156)	641	268
Income tax provision	77	(39)	154	64
Net income (loss)	244	(117)	487	204
Foreign Currency Translation Adjustments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income	(3)	(151)	(3)	(151)	(12)	(31)	(174)	(107)
Other comprehensive income (loss) before reclassifications	9	23	28	(44)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	0	0
Other comprehensive income (loss), net of tax	9	23	28	(44)
Other
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income	(24)	(26)	(24)	(26)	(24)	(23)	(26)	(26)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	(1)	0
Other comprehensive income (loss), net of tax	0	0	(1)	0
Other | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) from continuing operations before income taxes	0	0	1	0
Income tax provision	0	0	0	0
Net income (loss)	0	0	1	0
Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income	1,792	3,981	1,792	3,981	$ 1,783	$ 3,494	$ 3,679	$ 1,156
Other comprehensive income (loss) before reclassifications	253	185	(1,211)	3,037
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(244)	117	(491)	(204)
Other comprehensive income (loss), net of tax	$ 9	$ 302	$ (1,702)	$ 2,833