Fair Value - Schedule of Fair Value Measurements, Assets, Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	$ 2,792	$ 2,123	$ 2,756	$ 1,288
Total realized and unrealized gain (losses) recorded in revenue	(2)	(1)	(7)	(2)
Total realized and unrealized gain (losses) recorded in other comprehensive income	61	(29)	27	(30)
Purchases	672	104	861	914
Sales	(34)	0	(95)	0
Settlements	(30)	(98)	(83)	(275)
Transfers into Level 3	50	230	50	446
Transfers out of Level 3	0	(162)	0	(174)
Fair value, end of period	3,509	2,167	3,509	2,167
Change in unrealized gains (losses) related to financial instruments held	(4)	0	(4)	0
Derivative instruments, assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	2	11	4	4
Total realized and unrealized gain (losses) recorded in revenue	(2)	(1)	(7)	(3)
Total realized and unrealized gain (losses) recorded in other comprehensive income	0	0	0	0
Purchases	9	5	10	14
Sales	0	0	0	0
Settlements	(3)	(1)	(1)	(1)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Fair value, end of period	6	14	6	14
Change in unrealized gains (losses) related to financial instruments held	(4)	0	(4)	0
Foreign exchange contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	2	11	4	4
Total realized and unrealized gain (losses) recorded in revenue	(2)	(1)	(7)	(3)
Total realized and unrealized gain (losses) recorded in other comprehensive income	0	0	0	0
Purchases	9	5	10	14
Sales	0	0	0	0
Settlements	(3)	(1)	(1)	(1)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Fair value, end of period	6	14	6	14
Change in unrealized gains (losses) related to financial instruments held	(4)	0	(4)	0
US Treasury and federal agencies, mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period		123		0
Total realized and unrealized gain (losses) recorded in revenue		0		0
Total realized and unrealized gain (losses) recorded in other comprehensive income		0		0
Purchases		0		123
Sales		0		0
Settlements		0		0
Transfers into Level 3		0		0
Transfers out of Level 3		(123)		(123)
Fair value, end of period		0		0
Asset-backed securities, collateralized loan obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	1,869	1,222	1,820	593
Total realized and unrealized gain (losses) recorded in revenue	0	0	0	1
Total realized and unrealized gain (losses) recorded in other comprehensive income	14	0	(10)	0
Purchases	663	33	850	620
Sales	(34)	0	(95)	0
Settlements	(24)	(97)	(77)	(272)
Transfers into Level 3	50	230	50	446
Transfers out of Level 3	0	0	0	0
Fair value, end of period	2,538	1,388	2,538	1,388
Asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	1,869	1,222	1,820	593
Total realized and unrealized gain (losses) recorded in revenue	0	0	0	1
Total realized and unrealized gain (losses) recorded in other comprehensive income	14	0	(10)	0
Purchases	663	33	850	620
Sales	(34)	0	(95)	0
Settlements	(24)	(97)	(77)	(272)
Transfers into Level 3	50	230	50	446
Transfers out of Level 3	0	0	0	0
Fair value, end of period	2,538	1,388	2,538	1,388
Non-U.S. debt securities, asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	876	721	887	631
Total realized and unrealized gain (losses) recorded in revenue	0	0	0	0
Total realized and unrealized gain (losses) recorded in other comprehensive income	45	(27)	35	(28)
Purchases	0	66	1	157
Sales	0	0	0	0
Settlements	(3)	0	(5)	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	(39)	0	(39)
Fair value, end of period	918	721	918	721
Non-U.S. debt securities, other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	45	46	45	58
Total realized and unrealized gain (losses) recorded in revenue	0	0	0	0
Total realized and unrealized gain (losses) recorded in other comprehensive income	2	(2)	2	(2)
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	(12)
Fair value, end of period	47	44	47	44
Total non-U.S. debt securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	921	767	932	689
Total realized and unrealized gain (losses) recorded in revenue	0	0	0	0
Total realized and unrealized gain (losses) recorded in other comprehensive income	47	(29)	37	(30)
Purchases	0	66	1	157
Sales	0	0	0	0
Settlements	(3)	0	(5)	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	(39)	0	(51)
Fair value, end of period	965	765	965	765
Collateralized mortgage obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period				2
Total realized and unrealized gain (losses) recorded in revenue				0
Total realized and unrealized gain (losses) recorded in other comprehensive income				0
Purchases				0
Sales				0
Settlements				(2)
Transfers into Level 3				0
Transfers out of Level 3				0
Fair value, end of period		0		0
Investment securities available-for-sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	2,790	2,112	2,752	1,284
Total realized and unrealized gain (losses) recorded in revenue	0	0	0	1
Total realized and unrealized gain (losses) recorded in other comprehensive income	61	(29)	27	(30)
Purchases	663	99	851	900
Sales	(34)	0	(95)	0
Settlements	(27)	(97)	(82)	(274)
Transfers into Level 3	50	230	50	446
Transfers out of Level 3	0	(162)	0	(174)
Fair value, end of period	$ 3,503	$ 2,153	$ 3,503	$ 2,153