Fair Value - Schedule of Fair Value Measurements, Assets, Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	$ 2,722	$ 1,344	$ 2,756	$ 1,288
Total realized and unrealized gain (losses) recorded in revenue	(17)	(3)	(6)	(4)
Total realized and unrealized gain (losses) recorded in other comprehensive income	115	5	(34)	1
Purchases	13	670	194	814
Sales	(19)	0	(61)	0
Settlements	(22)	(109)	(57)	(180)
Transfers into Level 3	0	216	0	216
Transfers out of Level 3	0	0	0	(12)
Fair value, end of period	2,792	2,123	2,792	2,123
Change in unrealized gains (losses) related to financial instruments held	(9)	(2)	(3)	(2)
Derivative instruments, assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	17	4	4	4
Total realized and unrealized gain (losses) recorded in revenue	(17)	(3)	(6)	(5)
Total realized and unrealized gain (losses) recorded in other comprehensive income	0	0	0	0
Purchases	2	10	5	12
Sales	0	0	0	0
Settlements	0	0	(1)	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Fair value, end of period	2	11	2	11
Change in unrealized gains (losses) related to financial instruments held	(9)	(2)	(3)	(2)
Foreign exchange contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	17	4	4	4
Total realized and unrealized gain (losses) recorded in revenue	(17)	(3)	(6)	(5)
Total realized and unrealized gain (losses) recorded in other comprehensive income	0	0	0	0
Purchases	2	10	5	12
Sales	0	0	0	0
Settlements	0	0	(1)	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Fair value, end of period	2	11	2	11
Change in unrealized gains (losses) related to financial instruments held	(9)	(2)	(3)	(2)
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		0		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		123		123
Sales		0		0
Settlements		0		0
Transfers into Level 3		0		0
Transfers out of Level 3		0		0
Fair value, end of period		123		123
Asset-backed securities, collateralized loan obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	1,841	668	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	59	2	(24)	0
Purchases	10	455	188	587
Sales	(19)	0	(61)	0
Settlements	(22)	(119)	(54)	(175)
Transfers into Level 3	0	216	0	216
Transfers out of Level 3	0	0	0	0
Fair value, end of period	1,869	1,222	1,869	1,222
Asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	1,841	668	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	59	2	(24)	0
Purchases	10	455	188	587
Sales	(19)	0	(61)	0
Settlements	(22)	(119)	(54)	(175)
Transfers into Level 3	0	216	0	216
Transfers out of Level 3	0	0	0	0
Fair value, end of period	1,869	1,222	1,869	1,222
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	820	627	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	55	3	(10)	1
Purchases	1	82	1	92
Sales	0	0	0	0
Settlements	0	9	(2)	(3)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Fair value, end of period	876	721	876	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	44	45	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	1	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	1	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	(12)
Fair value, end of period	45	46	45	46
Total non-U.S. debt securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	864	672	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	56	3	(10)	1
Purchases	1	82	1	92
Sales	0	0	0	0
Settlements	0	10	(2)	(3)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	(12)
Fair value, end of period	921	767	921	767
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	2,705	1,340	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	115	5	(34)	1
Purchases	11	660	189	802
Sales	(19)	0	(61)	0
Settlements	(22)	(109)	(56)	(180)
Transfers into Level 3	0	216	0	216
Transfers out of Level 3	0	0	0	(12)
Fair value, end of period	$ 2,790	$ 2,112	$ 2,790	$ 2,112