Stockholders' Equity - Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Before Tax
Net unrealized gains (losses) on securities available for sale	$ (1,512)	$ 1,610
Net unrealized gains (losses) on hedging relationships	(766)	1,808
Foreign currency translation adjustments	13	(21)
Other	(1)	0
Other comprehensive income (loss), before tax	(2,266)	3,397
Provision (Benefit)
Net unrealized gains (losses) on securities available for sale	(364)	386
Net unrealized gains (losses) on hedging relationships	(185)	434
Foreign currency translation adjustments	(6)	46
Other	0	0
Other comprehensive income (loss), provision (benefit)	(555)	866
After Tax
Net unrealized gains (losses) on securities available for sale	(1,148)	1,224
Net unrealized gains (losses) on hedging relationships	(581)	1,374
Foreign currency translation adjustments	19	(67)
Other	(1)	0
Other comprehensive income (loss), net of tax	$ (1,711)	$ 2,531