Fair Value Measurement Fair Value Measurement - Schedule of Level 3 Inputs Reconciliation for Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 615	$ 1,205	$ 3,330
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	22	35	64
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	9	0	74
Purchases	420	142	1,214
Sales	0	(246)	(248)
Issuances	0	0	0
Settlements	(122)	(135)	(320)
Transfers Into Level 3	444	343	474
Transfers Out of Level 3	(810)	(729)	(3,383)
Ending balance	578	615	1,205
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	32	36	69
Corporate debt securities guaranteed by U.S. government agencies
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	333	927
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income		(1)	(5)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI		6	20
Purchases		0	0
Sales		(226)	(248)
Issuances		0	0
Settlements		(12)	(63)
Transfers Into Level 3		0	64
Transfers Out of Level 3		(100)	(362)
Ending balance		0	333
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held		0	0
RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	504	561	1,304
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	31	35	65
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	9	(3)	39
Purchases	110	0	1,022
Sales	0	0	0
Issuances	0	0	0
Settlements	(98)	(63)	(171)
Transfers Into Level 3	380	343	259
Transfers Out of Level 3	(418)	(369)	(1,957)
Ending balance	518	504	561
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	32	36	64
CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	97	228	739
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	0	0	0
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	(1)	3
Purchases	266	138	192
Sales	0	0	0
Issuances	0	0	0
Settlements	(14)	(52)	(75)
Transfers Into Level 3	64	0	66
Transfers Out of Level 3	(362)	(216)	(697)
Ending balance	51	97	228
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	0	0	0
Other ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	65	343
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	0	1	5
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	(2)	12
Purchases	30	0	0
Sales	0	(20)	0
Issuances	0	0	0
Settlements	0	0	(3)
Transfers Into Level 3	0	0	75
Transfers Out of Level 3	(30)	(44)	(367)
Ending balance	0	0	65
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	0	0	5
Other securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	14	18	17
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(9)	0	(1)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0	0
Purchases	14	4	0
Sales	0	0	0
Issuances	0	0	0
Settlements	(10)	(8)	(8)
Transfers Into Level 3	0	0	10
Transfers Out of Level 3	0	0	0
Ending balance	9	14	18
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	0	0	0
Consumer MSRs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	68	53	69
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(5)	(1)	(27)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0	0
Purchases	0	0	0
Sales	0	0	0
Issuances	23	22	15
Settlements	(6)	(6)	(4)
Transfers Into Level 3	0	0	0
Transfers Out of Level 3	0	0	0
Ending balance	80	68	53
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	(5)	(1)	(27)
Derivative Financial Instruments, Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	57	66	50
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	12	14	20
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0	0
Purchases	0	0	0
Sales	0	0	0
Issuances	69	49	20
Settlements	(73)	(59)	(21)
Transfers Into Level 3	0	0	0
Transfers Out of Level 3	(18)	(13)	3
Ending balance	47	57	66
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	12	14	19
Retained interest in securitizations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	211	221	199
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(10)	(10)	22
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0	0
Purchases	0	0	0
Sales	0	0	0
Issuances	0	0	0
Settlements	0	0	0
Transfers Into Level 3	0	0	0
Transfers Out of Level 3	0	0	0
Ending balance	201	211	221
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	$ (10)	$ (10)	$ 22