Fair Value - Schedule of Fair Value Measurements, Assets, Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	$ 5,356	$ 6,069	$ 5,447	$ 7,564
Recorded in Revenue, Assets	(83)	9	71	18
Recorded in Other Comprehensive Income, Assets	(7)	4	(18)	(1)
Purchases, Assets	10	66	476	155
Sales, Assets	(508)	0	(508)	(7)
Settlements, Assets	(366)	(340)	(718)	(705)
Transfers into Level 3, Assets	97		97
Transfers out of Level 3, Assets	(458)	(52)	(806)	(1,268)
Fair value as of end of period	4,041	5,756	4,041	5,756
Change in Unrealized Gains (Losses) Related to Financial Instruments Held as of period end	(30)	(4)	12	(7)
Derivative instruments, assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	185	6	81	19
Recorded in Revenue, Assets	(96)	(6)	45	(15)
Recorded in Other Comprehensive Income, Assets	0	0	0	0
Purchases, Assets	10	11	29	15
Sales, Assets	0	0	0	0
Settlements, Assets	(39)	(1)	(95)	(9)
Transfers into Level 3, Assets	0		0
Transfers out of Level 3, Assets	0	0	0	0
Fair value as of end of period	60	10	60	10
Change in Unrealized Gains (Losses) Related to Financial Instruments Held as of period end	(30)	(4)	12	(7)
Foreign exchange contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	185	6	81	19
Recorded in Revenue, Assets	(96)	(6)	$ 45	(15)
Recorded in Other Comprehensive Income, Assets	0	0		0
Purchases, Assets	10	11	$ 29	15
Sales, Assets	0	0		0
Settlements, Assets	(39)	(1)	$ (95)	(9)
Transfers into Level 3, Assets	0
Transfers out of Level 3, Assets	0	0		0
Fair value as of end of period	60	10	$ 60	10
Change in Unrealized Gains (Losses) Related to Financial Instruments Held as of period end	(30)	(4)	12	(7)
Investment securities available for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	5,171	6,063	5,366	7,545
Recorded in Revenue, Assets	13	15	26	33
Recorded in Other Comprehensive Income, Assets	(7)	4	(18)	(1)
Purchases, Assets	0	55	447	140
Sales, Assets	(508)	0	(508)	(7)
Settlements, Assets	(327)	(339)	(623)	(696)
Transfers into Level 3, Assets	97		97
Transfers out of Level 3, Assets	(458)	(52)	(806)	(1,268)
Fair value as of end of period	3,981	5,746	3,981	5,746
Investment securities available for sale | US Treasury and federal agencies, mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period		100		716
Recorded in Revenue, Assets		0		0
Recorded in Other Comprehensive Income, Assets		0		0
Purchases, Assets		0		0
Sales, Assets		0		0
Settlements, Assets		(4)		(9)
Transfers out of Level 3, Assets		0		(611)
Fair value as of end of period		96		96
Investment securities available for sale | Total asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	3,890	4,637	4,039	4,979
Recorded in Revenue, Assets	13	14	25	30
Recorded in Other Comprehensive Income, Assets	(6)	1	(17)	(3)
Purchases, Assets	0	0	0	6
Sales, Assets	(420)	0	(420)	0
Settlements, Assets	(288)	(269)	(439)	(550)
Transfers into Level 3, Assets	0		0
Transfers out of Level 3, Assets	(22)	0	(21)	(79)
Fair value as of end of period	3,167	4,383	3,167	4,383
Investment securities available for sale | Asset-backed securities, student loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	257	333	259	423
Recorded in Revenue, Assets	0	1	0	1
Recorded in Other Comprehensive Income, Assets	0	2	1	3
Purchases, Assets	0	0	0	0
Sales, Assets	0	0	0	0
Settlements, Assets	(1)	(14)	(5)	(26)
Transfers into Level 3, Assets	0		0
Transfers out of Level 3, Assets	(22)	0	(21)	(79)
Fair value as of end of period	234	322	234	322
Investment securities available for sale | Asset-backed securities, credit cards
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period				24
Recorded in Revenue, Assets				0
Recorded in Other Comprehensive Income, Assets				0
Purchases, Assets				0
Sales, Assets				0
Settlements, Assets				(24)
Transfers out of Level 3, Assets				0
Fair value as of end of period		0		0
Investment securities available for sale | Asset-backed securities, other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	3,633	4,304	3,780	4,532
Recorded in Revenue, Assets	13	13	25	29
Recorded in Other Comprehensive Income, Assets	(6)	(1)	(18)	(6)
Purchases, Assets	0	0	0	6
Sales, Assets	(420)	0	(420)	0
Settlements, Assets	(287)	(255)	(434)	(500)
Transfers into Level 3, Assets	0		0
Transfers out of Level 3, Assets	0	0	0	0
Fair value as of end of period	2,933	4,061	2,933	4,061
Investment securities available for sale | Total non-U.S. debt securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	713	1,074	666	1,637
Recorded in Revenue, Assets	0	1	1	3
Recorded in Other Comprehensive Income, Assets	0	2	1	2
Purchases, Assets	0	55	154	54
Sales, Assets	0	0	0	(1)
Settlements, Assets	(9)	(59)	(118)	(123)
Transfers into Level 3, Assets	97		97
Transfers out of Level 3, Assets	(247)	(52)	(247)	(551)
Fair value as of end of period	554	1,021	554	1,021
Investment securities available for sale | Non-U.S. debt securities, mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	43		0	375
Recorded in Revenue, Assets	0		0	0
Recorded in Other Comprehensive Income, Assets	0		0	0
Purchases, Assets	0		43	0
Sales, Assets	0		0	0
Settlements, Assets	0		0	0
Transfers into Level 3, Assets	97		97
Transfers out of Level 3, Assets	(43)		(43)	(375)
Fair value as of end of period	97	0	97	0
Investment securities available for sale | Non-U.S. debt securities, asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	228	612	295	798
Recorded in Revenue, Assets	0	1	1	3
Recorded in Other Comprehensive Income, Assets	0	1	0	1
Purchases, Assets	0	0	0	0
Sales, Assets	0	0	0	0
Settlements, Assets	(18)	(56)	(86)	(120)
Transfers into Level 3, Assets	0		0
Transfers out of Level 3, Assets	(17)	(52)	(17)	(176)
Fair value as of end of period	193	506	193	506
Investment securities available for sale | Non-U.S. debt securities, other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	442	462	371	464
Recorded in Revenue, Assets	0	0	0	0
Recorded in Other Comprehensive Income, Assets	0	1	1	1
Purchases, Assets	0	55	111	54
Sales, Assets	0	0	0	(1)
Settlements, Assets	9	(3)	(32)	(3)
Transfers into Level 3, Assets	0		0
Transfers out of Level 3, Assets	(187)	0	(187)	0
Fair value as of end of period	264	515	264	515
Investment securities available for sale | State and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	37	42	38	43
Recorded in Revenue, Assets	0	0	0	0
Recorded in Other Comprehensive Income, Assets	0	0	(1)	(1)
Purchases, Assets	0	0	0	0
Sales, Assets	0	0	0	0
Settlements, Assets	(1)	(1)	(1)	(1)
Transfers into Level 3, Assets	0		0
Transfers out of Level 3, Assets	0	0	0	0
Fair value as of end of period	36	41	36	41
Investment securities available for sale | Collateralized mortgage obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	522	202	614	162
Recorded in Revenue, Assets	0	0	0	0
Recorded in Other Comprehensive Income, Assets	(1)	0	(1)	0
Purchases, Assets	0	0	293	80
Sales, Assets	(88)	0	(88)	(6)
Settlements, Assets	(29)	(6)	(65)	(13)
Transfers into Level 3, Assets	0		0
Transfers out of Level 3, Assets	(189)	0	(538)	(27)
Fair value as of end of period	215	196	215	196
Investment securities available for sale | Other U.S. debt securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	9	8	9	8
Recorded in Revenue, Assets	0	0	0	0
Recorded in Other Comprehensive Income, Assets	0	1	0	1
Purchases, Assets	0	0	0	0
Sales, Assets	0	0	0	0
Settlements, Assets	0	0	0	0
Transfers into Level 3, Assets	0		0
Transfers out of Level 3, Assets	0	0	0	0
Fair value as of end of period	$ 9	$ 9	$ 9	$ 9