Credit Quality - Summary of Subsequent Defaults (Details) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Financing Receivable, Modifications [Line Items]
Number of contracts	146	183	825	679
Recorded Investment in Loans Modified in a TDR During the Period	$ 13	$ 37	$ 54	$ 88
Commercial Portfolio Segment \| Commercial and Industrial Loans
Financing Receivable, Modifications [Line Items]
Number of contracts	1	5	8	8
Recorded Investment in Loans Modified in a TDR During the Period	$ 3	$ 32	$ 20	$ 61
Commercial Portfolio Segment \| Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Modifications [Line Items]
Number of contracts	2		4	2
Recorded Investment in Loans Modified in a TDR During the Period	$ 0		$ 1	$ 0
Residential Mortgage Loans
Financing Receivable, Modifications [Line Items]
Number of contracts	67	28	196	138
Recorded Investment in Loans Modified in a TDR During the Period	$ 10	$ 4	$ 30	$ 24
Consumer Portfolio Segment \| Home Equity
Financing Receivable, Modifications [Line Items]
Number of contracts	7	4	12	6
Recorded Investment in Loans Modified in a TDR During the Period	$ 0	$ 0	$ 0	$ 0
Consumer Portfolio Segment \| Credit Card
Financing Receivable, Modifications [Line Items]
Number of contracts	69	146	605	525
Recorded Investment in Loans Modified in a TDR During the Period	$ 0	$ 1	$ 3	$ 3

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Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953682-111524

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Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953682-111524

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