Fair Value Measurement Fair Value Measurement - Schedule of Level 3 Inputs Reconciliation for Assets (Details) - USD ($) $ in Millions	12 Months Ended
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	$ 1,205	$ 3,330
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	35	64
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	74
Purchases	142	1,214
Sales	(246)	(248)
Issuances	0	0
Settlements	(135)	(320)
Transfers Into Level 3	343	474
Transfers Out of Level 3	(729)	(3,383)
Ending balance	615	1,205
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	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	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	561	1,304
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	35	65
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	(3)	39
Purchases	0	1,022
Sales	0	0
Issuances	0	0
Settlements	(63)	(171)
Transfers Into Level 3	343	259
Transfers Out of Level 3	(369)	(1,957)
Ending balance	504	561
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	36	64
CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	228	739
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	0	0
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	(1)	3
Purchases	138	192
Sales	0	0
Issuances	0	0
Settlements	(52)	(75)
Transfers Into Level 3	0	66
Transfers Out of Level 3	(216)	(697)
Ending balance	97	228
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	65	343
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	1	5
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	(2)	12
Purchases	0	0
Sales	(20)	0
Issuances	0	0
Settlements	0	(3)
Transfers Into Level 3	0	75
Transfers Out of Level 3	(44)	(367)
Ending balance	0	65
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	0	5
Other securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	18	17
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	0	(1)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0
Purchases	4	0
Sales	0	0
Issuances	0	0
Settlements	(8)	(8)
Transfers Into Level 3	0	10
Transfers Out of Level 3	0	0
Ending balance	14	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	53	69
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(1)	(27)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0
Purchases	0	0
Sales	0	0
Issuances	22	15
Settlements	(6)	(4)
Transfers Into Level 3	0	0
Transfers Out of Level 3	0	0
Ending balance	68	53
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	(1)	(27)
Derivative assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	66	50
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	14	20
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0
Purchases	0	0
Sales	0	0
Issuances	49	20
Settlements	(59)	(21)
Transfers Into Level 3	0	0
Transfers Out of Level 3	(13)	(3)
Ending balance	57	66
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	14	19
Retained interest in securitizations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	221	199
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(10)	22
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	211	221
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	$ (10)	$ 22

Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
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Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 2
-Subparagraph (c)(1a)
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Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Publisher FASB
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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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-Publisher FASB
-Name Accounting Standards Codification
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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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