Fair Value - Schedule of Fair Value Measurements, Assets, Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	$ 4,041	$ 5,756	$ 5,447	$ 7,564
Recorded in Revenue, Assets	17	64	97	79
Recorded in Other Comprehensive Income, Assets	(26)	(10)	(44)	(12)
Purchases, Assets	169	614	632	766
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	(686)	(74)	(1,194)	(81)
Settlements, Assets	(443)	(551)	(1,157)	(1,249)
Transfers into Level 3, Assets		76	97	76
Transfers out of Level 3, Assets	(146)	(332)	(952)	(1,600)
Fair value as of end of period	2,926	5,543	2,926	5,543
Change in Unrealized Gains (Losses) Related to Financial Instruments Held as of period end	0	40	0	35
Derivative instruments, assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	60	10	81	19
Recorded in Revenue, Assets	(5)	44	49	26
Recorded in Other Comprehensive Income, Assets	0	0	0	0
Purchases, Assets	1	22	17	32
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	0	0	0	0
Settlements, Assets	(35)	(8)	(126)	(9)
Transfers into Level 3, Assets		0	0	0
Transfers out of Level 3, Assets	0	0	0	0
Fair value as of end of period	21	68	21	68
Change in Unrealized Gains (Losses) Related to Financial Instruments Held as of period end	0	40	0	35
Foreign exchange contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	60	10	81	19
Recorded in Revenue, Assets	(5)	44	49	26
Recorded in Other Comprehensive Income, Assets	0	0	0	0
Purchases, Assets	1	22	17	32
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	0	0	0	0
Settlements, Assets	(35)	(8)	(126)	(9)
Transfers into Level 3, Assets		0	0	0
Transfers out of Level 3, Assets	0	0	0	0
Fair value as of end of period	21	68	21	68
Change in Unrealized Gains (Losses) Related to Financial Instruments Held as of period end	0	40	0	35
Other Assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of beginning of period	0
Recorded in Revenue, Assets	0
Recorded in Other Comprehensive Income, Assets	0
Purchases, Assets	0
Sales, Assets	0
Settlements, Assets	0
Transfers out of Level 3, Assets	0
Fair value as of end of period	0		0
Change in Unrealized Gains (Losses) Related to Financial Instruments Held as of period end	0
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	3,981	5,746	5,366	7,545
Recorded in Revenue, Assets	22	20	48	53
Recorded in Other Comprehensive Income, Assets	(26)	(10)	(44)	(12)
Purchases, Assets	168	592	615	734
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	(686)	(74)	(1,194)	(81)
Settlements, Assets	(408)	(543)	(1,031)	(1,240)
Transfers into Level 3, Assets		76	97	76
Transfers out of Level 3, Assets	(146)	(332)	(952)	(1,600)
Fair value as of end of period	2,905	5,475	2,905	5,475
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		96		716
Recorded in Revenue, Assets		0		0
Recorded in Other Comprehensive Income, Assets		0		0
Purchases, Assets		168		168
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets		0		0
Settlements, Assets		(4)		(14)
Transfers into Level 3, Assets		0		0
Transfers out of Level 3, Assets		0		(610)
Fair value as of end of period		260		260
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	3,167	4,383	4,039	4,979
Recorded in Revenue, Assets	22	18	47	47
Recorded in Other Comprehensive Income, Assets	(22)	(9)	(39)	(12)
Purchases, Assets	0	299	0	306
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	(686)	(74)	(1,106)	(74)
Settlements, Assets	(308)	(407)	(747)	(957)
Transfers into Level 3, Assets		0	0	0
Transfers out of Level 3, Assets	0	0	(21)	(79)
Fair value as of end of period	2,173	4,210	2,173	4,210
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	234	$ 322	259	423
Recorded in Revenue, Assets	0		0	1
Recorded in Other Comprehensive Income, Assets	(3)	$ (1)	(2)	2
Purchases, Assets	0	24	0	24
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	0	(74)	0	(74)
Settlements, Assets	(1)	(5)	(6)	(31)
Transfers into Level 3, Assets		0	0	0
Transfers out of Level 3, Assets	0	0	(21)	(79)
Fair value as of end of period	230	266	230	266
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
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets				0
Settlements, Assets				(24)
Transfers into Level 3, Assets				0
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	2,933	4,061	3,780	4,532
Recorded in Revenue, Assets	22	18	47	46
Recorded in Other Comprehensive Income, Assets	(19)	(8)	(37)	(14)
Purchases, Assets	0	275	0	282
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	(686)	0	(1,106)	0
Settlements, Assets	(307)	(402)	(741)	(902)
Transfers into Level 3, Assets		0	0	0
Transfers out of Level 3, Assets	0	0	0	0
Fair value as of end of period	1,943	3,944	1,943	3,944
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	554	1,021	666	1,637
Recorded in Revenue, Assets	0	2	1	5
Recorded in Other Comprehensive Income, Assets	(2)	(1)	(1)	0
Purchases, Assets	168	0	322	55
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	0	0	0	(1)
Settlements, Assets	(83)	(124)	(201)	(247)
Transfers into Level 3, Assets		76	97	76
Transfers out of Level 3, Assets	(97)	(252)	(344)	(803)
Fair value as of end of period	540	722	540	722
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	97		0	375
Recorded in Revenue, Assets	0		0	0
Recorded in Other Comprehensive Income, Assets	0		0	0
Purchases, Assets	0		43	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	0		0	0
Settlements, Assets	0		0	0
Transfers into Level 3, Assets			97	0
Transfers out of Level 3, Assets	(97)		(140)	(375)
Fair value as of end of period	0	0	0	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	193	506	295	798
Recorded in Revenue, Assets	0	2	1	5
Recorded in Other Comprehensive Income, Assets	(1)	(1)	(1)	0
Purchases, Assets	168	0	168	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	0	0	0	0
Settlements, Assets	(83)	(99)	(169)	(219)
Transfers into Level 3, Assets		76	0	76
Transfers out of Level 3, Assets	0	(60)	(17)	(236)
Fair value as of end of period	277	424	277	424
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	264	515	371	464
Recorded in Revenue, Assets	0	0	0	0
Recorded in Other Comprehensive Income, Assets	(1)	0	0	0
Purchases, Assets	0	0	111	55
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	0	0	0	(1)
Settlements, Assets	0	(25)	(32)	(28)
Transfers into Level 3, Assets		0	0	0
Transfers out of Level 3, Assets	0	(192)	(187)	(192)
Fair value as of end of period	263	298	263	298
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	36	41	38	43
Recorded in Revenue, Assets	0	0	0	1
Recorded in Other Comprehensive Income, Assets	(1)	0	(2)	(1)
Purchases, Assets	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	0	0	0	0
Settlements, Assets	0	0	(1)	(2)
Transfers into Level 3, Assets		0	0	0
Transfers out of Level 3, Assets	0	0	0	0
Fair value as of end of period	35	41	35	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	215	196	614	162
Recorded in Revenue, Assets	0	0	0	0
Recorded in Other Comprehensive Income, Assets	(1)	0	(2)	1
Purchases, Assets	0	125	293	205
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	0	0	(88)	(6)
Settlements, Assets	(17)	(7)	(82)	(20)
Transfers into Level 3, Assets		0	0	0
Transfers out of Level 3, Assets	(49)	(80)	(587)	(108)
Fair value as of end of period	148	234	148	234
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	9	9	8
Recorded in Revenue, Assets	0	0	0	0
Recorded in Other Comprehensive Income, Assets	0	0	0	0
Purchases, Assets	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0
Sales, Assets	0	0	0	0
Settlements, Assets	0	(1)	0	0
Transfers into Level 3, Assets		0	0	0
Transfers out of Level 3, Assets	0	0	0	0
Fair value as of end of period	$ 9	$ 8	$ 9	$ 8