Goodwill and Mortgage Servicing Rights - Key Economic Assumptions (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Weighted-average prepayment speed assumption (“CPR”)	8.43%	9.35%
Impact on fair value of 10% adverse change	$ (195)	$ (221)
Impact on fair value of 20% adverse change	$ (379)	$ (427)
Weighted-average option adjusted spread	8.72%	9.04%
Impact on fair value of a 100 basis point adverse change	$ (245)	$ (250)
Impact on fair value of a 200 basis point adverse change	$ (472)	$ (481)

Weighted-average option adjusted spread.

No definition available.

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- Definition

Impact on fair value of 100 basis points adverse change in the weighted-average option adjusted spread.

+ References

No definition available.

+ Details

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- Definition

Impact on fair value of 200 basis points adverse change in the weighted-average option adjusted spread.

+ References

No definition available.

+ Details

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- References

No definition available.

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- Definition

The hypothetical financial impact of a 10 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82924980&loc=d3e107314-111719

+ Details

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- Definition

The hypothetical financial impact of a 20 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

+ Details

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- Definition

A specified percentage variance in the prepayment speed assumption in the determination of fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities).

+ References

+ Details

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