Fair Value Measurement Fair Value Measurement - Schedule of Level 3 Inputs Reconciliation for Assets (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Available-for-sale Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 615	$ 1,205
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	6	7
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	(4)	12
Purchases	123	0
Sales	0	(88)
Issuances	0	0
Settlements	(24)	(42)
Transfers Into Level 3	191	85
Transfers Out of Level 3	(110)	(253)
Ending balance	797	926
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	6	9
Corporate debt securities guaranteed by U.S. government agencies
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		333
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income		(2)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI		5
Purchases		0
Sales		(68)
Issuances		0
Settlements		(8)
Transfers Into Level 3		0
Transfers Out of Level 3		(88)
Ending balance		172
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held		0
RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	504	561
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	6	8
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	(5)	8
Purchases	0	0
Sales	0	0
Issuances	0	0
Settlements	(17)	(13)
Transfers Into Level 3	127	85
Transfers Out of Level 3	(110)	(94)
Ending balance	505	555
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	6	9
CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	97	228
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	0	0
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	1	1
Purchases	93	0
Sales	0	0
Issuances	0	0
Settlements	(4)	(21)
Transfers Into Level 3	64	0
Transfers Out of Level 3	0	(34)
Ending balance	251	174
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	0	0
Other ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	65
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	0	1
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	(2)
Purchases	30	0
Sales	0	(20)
Issuances	0	0
Settlements	0	0
Transfers Into Level 3	0	0
Transfers Out of Level 3	0	(37)
Ending balance	30	7
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	14	18
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
Sales	0	0
Issuances	0	0
Settlements	(3)	0
Transfers Into Level 3	0	0
Transfers Out of Level 3	0	0
Ending balance	11	18
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	0	0
Consumer MSRs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	68	53
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(12)	(3)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0
Purchases	0	0
Sales	0	0
Issuances	4	4
Settlements	(1)	(1)
Transfers Into Level 3	0	0
Transfers Out of Level 3	0	0
Ending balance	59	53
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	(12)	(3)
Derivative assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	57	66
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	19	11
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0
Purchases	0	0
Sales	0	0
Issuances	12	9
Settlements	(11)	(12)
Transfers Into Level 3	0	0
Transfers Out of Level 3	(6)	(1)
Ending balance	71	73
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	19	11
Retained interest in securitizations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	211	221
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(10)	2
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0
Purchases	0	0
Sales	0	0
Issuances	0	0
Settlements	0	0
Transfers Into Level 3	0	0
Transfers Out of Level 3	0	0
Ending balance	201	223
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	$ (10)	$ 2