Fair Value Measurement Fair Value Measurement - Schedule of Level 3 Inputs Reconciliation for Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Available-for-sale Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 745	$ 2,219	$ 1,205	$ 3,330
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	10	11	29	51
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	(1)	7	2	73
Purchases	28	200	114	1,214
Sales	(36)	(91)	(204)	(203)
Issuances	0	0	0	0
Settlements	(37)	(81)	(111)	(284)
Transfers Into Level 3	93	88	285	384
Transfers Out of Level 3	(123)	(887)	(641)	(3,099)
Ending balance	679	1,466	679	1,466
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	10	15	29	55
Corporate debt securities guaranteed by U.S. government agencies
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	91	739	333	927
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	1	(5)	0	(5)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	1	3	6	18
Purchases	0	0	0	0
Sales	(36)	(91)	(184)	(203)
Issuances	0	0	0	0
Settlements	(2)	(16)	(12)	(55)
Transfers Into Level 3	0	0	0	64
Transfers Out of Level 3	(12)	(246)	(100)	(362)
Ending balance	43	384	43	384
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	0	(1)	0	(1)
RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	459	836	561	1,304
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	9	16	28	53
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	(1)	3	(2)	39
Purchases	0	42	0	1,022
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	(19)	(24)	(46)	(156)
Transfers Into Level 3	93	79	285	199
Transfers Out of Level 3	(22)	(295)	(307)	(1,804)
Ending balance	519	657	519	657
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	10	16	29	53
CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	170	449	228	739
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	0	0	0	0
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	(1)	(2)	0	3
Purchases	28	158	114	192
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	(10)	(34)	(47)	(64)
Transfers Into Level 3	0	0	0	66
Transfers Out of Level 3	(82)	(268)	(190)	(633)
Ending balance	105	303	105	303
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	7	175	65	343
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	0	1	1	4
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	3	(2)	13
Purchases	0	0	0	0
Sales	0	0	(20)	0
Issuances	0	0	0	0
Settlements	0	0	0	(2)
Transfers Into Level 3	0	9	0	52
Transfers Out of Level 3	(7)	(78)	(44)	(300)
Ending balance	0	110	0	110
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	0	1	0	4
Other securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	18	20	18	17
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	0	(1)	0	(1)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0	0	0
Purchases	0	0		0
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	(6)	(7)	(6)	(7)
Transfers Into Level 3	0	0	0	3
Transfers Out of Level 3	0	0	0	0
Ending balance	12	12	12	12
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	0	(1)	0	(1)
Consumer MSRs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	65	57	53	69
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(7)	(2)	(2)	(19)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	7	4	17	11
Settlements	(2)	(1)	(5)	(3)
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	0	0	0	0
Ending balance	63	58	63	58
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	(7)	(2)	(2)	(19)
Derivative assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	61	50	66	50
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	16	2	17	5
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	13	6	40	13
Settlements	(18)	(8)	(46)	(14)
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	(7)	1	(12)	(3)
Ending balance	65	51	65	51
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	16	2	17	5
Retained interest in securitizations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	220	195	221	199
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(6)	8	(7)	4
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	214	203	214	203
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	$ (6)	$ 8	$ (7)	$ 4