Derivative Financial Instruments - The Effect of Derivative Instruments on the Consolidated Statements of Income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Not designated as hedges
Not Designated as Hedges:
Pre-tax Gain (Loss) Recognized in Income	$ 39	$ 102	$ 87
Cash flow hedges \| Interest rate contracts
Cash Flow Hedges:
Pre-tax Gain (Loss) Recognized in OCI	10	(24)	(130)
Cash flow hedges \| Interest rate contracts \| Interest expense
Cash Flow Hedges:
Pre-tax Gain (Loss) Reclassified from AOCI into Income	(15)	(11)	(83)
Fair value hedges \| Interest rate contracts
Fair Value Hedges:
Pre-tax Gain (Loss) Recognized in Income	129	208	259
Fair value hedges \| Interest rate contracts \| Interest income
Fair Value Hedges:
Pre-tax Gain (Loss) Recognized in Income	(19)	(18)	(20)
Fair value hedges \| Interest rate contracts \| Interest expense
Fair Value Hedges:
Pre-tax Gain (Loss) Recognized in Income	148	226	279
Client-related and other risk management \| Interest rate contracts \| Other income \| Not designated as hedges
Not Designated as Hedges:
Pre-tax Gain (Loss) Recognized in Income	50	52	27
Client-related and other risk management \| Foreign exchange contracts \| Other income \| Not designated as hedges
Not Designated as Hedges:
Pre-tax Gain (Loss) Recognized in Income	1	11	21
Mortgage banking \| Interest rate contracts \| Mortgage banking income \| Not designated as hedges
Not Designated as Hedges:
Pre-tax Gain (Loss) Recognized in Income	(12)	8	7
MSRs \| Interest rate contracts \| Mortgage banking income \| Not designated as hedges
Not Designated as Hedges:
Pre-tax Gain (Loss) Recognized in Income	$ 0	$ 31	$ 32

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624177-113959

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The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

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Amount of gain (loss) included in earnings for the period from the increase (decrease) in fair value of interest rate derivatives not designated as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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