Stockholders' Equity - Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Before Tax
Net unrealized gains (losses) on securities available for sale	$ 1,659	$ 855	$ (605)
Net unrealized gains (losses) on hedging relationships	1,329	1,016	(98)
Foreign currency translation adjustments	56	54	9
Net changes in securities held to maturity	0	36	588
Other	4	17	(15)
Other comprehensive income (loss), before tax	3,048	1,978	(121)
Provision (Benefit)
Net unrealized gains (losses) on securities available for sale	400	205	(146)
Net unrealized gains (losses) on hedging relationships	321	244	(24)
Foreign currency translation adjustments	(20)	(16)	48
Net changes in securities held to maturity	0	10	141
Other	1	4	(4)
Other comprehensive income (loss), provision (benefit)	702	447	15
After Tax
Net unrealized gains (losses) on securities available for sale	1,259	650	(459)
Net unrealized gains (losses) on hedging relationships	1,008	772	(74)
Foreign currency translation adjustments	76	70	(39)
Net changes in securities held to maturity	0	26	447
Other	3	13	(11)
Other comprehensive income (loss), net of tax	$ 2,346	$ 1,531	$ (136)

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