Fair Value (Fair Value Option for Certain Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Option, Quantitative Disclosures [Line Items]
Carrying value at estimated fair value	$ 74,545	$ 67,102
Carrying value at estimated fair value	16,502	18,023
Consolidated Securitization Entities
Fair Value, Option, Quantitative Disclosures [Line Items]
Unpaid principal balance	88	121
Difference between estimated fair value and unpaid principal balance	48	51
Carrying value at estimated fair value	136	172
Loans in nonaccrual status	0	0
Loans more than 90 days past due	0	0
Loans in nonaccrual status or more than 90 days past due, or both - difference between aggregate estimate fair value and unpaid principal balance	0	0
Contractual principal balance	47	71
Difference between estimated fair value and contractual principal balance	(12)	(11)
Carrying value at estimated fair value	35	60
Residential Mortgage Loans - FVO
Fair Value, Option, Quantitative Disclosures [Line Items]
Unpaid principal balance	794	436
Difference between estimated fair value and unpaid principal balance	(228)	(122)
Carrying value at estimated fair value	566	314
Loans in nonaccrual status	214	122
Loans more than 90 days past due	137	72
Loans in nonaccrual status or more than 90 days past due, or both - difference between aggregate estimate fair value and unpaid principal balance	$ (150)	$ (52)

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Publisher FASB
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This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of loans and long-term receivables (other than securities categorized as trading, available-for-sale or held-to-maturity) that have contractual principal amounts and for which the fair value option has been elected.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (d)(1)
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This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of long-term debt instruments that have contractual principal amounts and for which the fair value option has been elected.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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This item represents the aggregate fair value of loans held as assets that are 90 days or more past due for which the fair value option has been elected.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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For loans held as assets for which the fair value option has been elected, this item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of those loans that are 90 days or more past due.

+ References

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This item represents the aggregate fair value of loans held as assets that are in nonaccrual status for which the fair value option has been elected, if the entity's policy is to recognize interest income separately from other changes in fair value.

+ References

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Amount of long-term debt and capital lease obligations including current maturities.

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- Definition

Total carrying amount of mortgage loans as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
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Amount of the contractual principal due at the origination of the mortgage loan (face amount).

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