Fair Value Measurement Fair Value Measurement - Schedule of Level 3 Inputs Reconciliation for Assets (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Available-for-sale Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 536	$ 797	$ 578	$ 615
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	8	7	17	13
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	10	12	18	8
Purchases	0	130	60	253
Sales	(5)	0	(5)	0
Issuances	0	0	0	0
Settlements	(25)	(37)	(48)	(61)
Transfers Into Level 3	159	80	212	271
Transfers Out of Level 3	(228)	(257)	(377)	(367)
Ending balance	455	732	455	732
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	8	8	17	14
RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	449	505	518	504
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	8	7	17	13
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	10	11	18	6
Purchases	0	59	0	59
Sales	(5)	0	(5)	0
Issuances	0	0	0	0
Settlements	(24)	(31)	(46)	(48)
Transfers Into Level 3	159	80	212	207
Transfers Out of Level 3	(168)	(76)	(285)	(186)
Ending balance	429	555	429	555
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	8	8	17	14
CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	78	251	51	97
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	0	0	0	0
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	1	0	2
Purchases	0	63	60	156
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	(1)	(6)	(2)	(10)
Transfers Into Level 3	0	0	0	64
Transfers Out of Level 3	(60)	(181)	(92)	(181)
Ending balance	17	128	17	128
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	0	0	0	0
Other ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		30		0
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income		0		0
Total Gains or (Losses) (Realized/Unrealized), Included in OCI		0		0
Purchases		0		30
Sales		0		0
Issuances		0		0
Settlements		0		0
Transfers Into Level 3		0		0
Transfers Out of Level 3		0		0
Ending balance		30		30
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held		0		0
Other securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	9	11	9	14
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	0	0	0	0
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0	0	0
Purchases		8		8
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	0	0	0	(3)
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	0	0	0	0
Ending balance	9	19	9	19
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	0	0	0	0
Consumer MSRs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	86	59	80	68
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(5)	(8)	(4)	(20)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	5	4	12	8
Settlements	(1)	(2)	(3)	(3)
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	0	0	0	0
Ending balance	85	53	85	53
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	(5)	(8)	(4)	(20)
Derivative Financial Instruments, Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	53	71	47	57
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	4	9	3	28
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	22	30	40	42
Settlements	(15)	(15)	(25)	(26)
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	(7)	(10)	(8)	(16)
Ending balance	57	85	57	85
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	4	9	3	28
Retained interest in securitizations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	195	201	201	211
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(7)	2	(13)	(8)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	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	0
Ending balance	188	203	188	203
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	$ (7)	$ 2	$ (13)	$ (8)