Variable Interest Entities - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Maximum exposure to loss	$ 3,547	$ 3,541
Structured note vehicles [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Maximum exposure to loss	$ 3,013	$ 3,013
Loans to Refinancing Special Purpose Entity [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity subordination in borrower's capital structure (percent)	15.00%
Financial guarantee of outstanding debt by borrowers' parent (percent)	25.00%

Equity Subordination in Borrower's Capital Structure, Percent

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- Definition

Financial Guarantee of Outstanding Debt by Borrowers' Parent, Percent

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph b
-URI http://asc.fasb.org/extlink&oid=77990344&loc=d3e5728-111685

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=77990344&loc=d3e5747-111685

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- Details

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- Details

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