Fair Value Measurement Fair Value Measurement - Schedule of Level 3 Inputs Reconciliation for Assets (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Available-for-sale Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 578	$ 615
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	9	6
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	8	(4)
Purchases	60	123
Sales	0	0
Issuances	0	0
Settlements	(23)	(24)
Transfers Into Level 3	53	191
Transfers Out of Level 3	(149)	(110)
Ending balance	536	797
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	9	6
RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	518	504
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	9	6
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	8	(5)
Purchases	0	0
Sales	0	0
Issuances	0	0
Settlements	(22)	(17)
Transfers Into Level 3	53	127
Transfers Out of Level 3	(117)	(110)
Ending balance	449	505
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	0	6
CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	51	97
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	0	0
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	1
Purchases	60	93
Sales	0	0
Issuances	0	0
Settlements	(1)	(4)
Transfers Into Level 3	0	64
Transfers Out of Level 3	(32)	0
Ending balance	78	251
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	9	0
Other ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		0
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income		0
Total Gains or (Losses) (Realized/Unrealized), Included in OCI		0
Purchases		30
Sales		0
Issuances		0
Settlements		0
Transfers Into Level 3		0
Transfers Out of Level 3		0
Ending balance		30
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held		0
Other securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	9	14
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	0	(3)
Transfers Into Level 3	0	0
Transfers Out of Level 3	0	0
Ending balance	9	11
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	80	68
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	1	(12)
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0
Purchases	0	0
Sales	0	0
Issuances	7	4
Settlements	(2)	(1)
Transfers Into Level 3	0	0
Transfers Out of Level 3	0	0
Ending balance	86	59
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	1	(12)
Derivative Financial Instruments, Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	47	57
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(1)	19
Total Gains or (Losses) (Realized/Unrealized), Included in OCI	0	0
Purchases	0	0
Sales	0	0
Issuances	18	12
Settlements	(10)	(11)
Transfers Into Level 3	0	0
Transfers Out of Level 3	(1)	(6)
Ending balance	53	71
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	(1)	19
Retained interest in securitizations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	201	211
Total Gains or (Losses) (Realized/Unrealized), Included in Net Income	(6)	(10)
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	195	201
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	$ (6)	$ (10)

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=66048111&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.

+ References

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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)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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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

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)(1a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

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

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)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&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

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)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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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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-Publisher FASB
-Name Accounting Standards Codification
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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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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.

+ References

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