Credit Quality (Summary of Subsequent Defaults) (Detail) $ in Millions	3 Months Ended
Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)
Financing Receivable, Modifications
Number of contracts	255	365
Recorded Investment in Loans Modified in a TDR During the Period	$ 13	$ 30
Commercial Portfolio Segment \| Commercial and Industrial Loans
Financing Receivable, Modifications
Number of contracts	2	2
Recorded Investment in Loans Modified in a TDR During the Period	$ 1	$ 16
Commercial Portfolio Segment \| Commercial Mortgage Loans, Owner-Occupied
Financing Receivable, Modifications
Number of contracts	1
Recorded Investment in Loans Modified in a TDR During the Period	$ 5
Residential Mortgage Loans
Financing Receivable, Modifications
Number of contracts	47	76
Recorded Investment in Loans Modified in a TDR During the Period	$ 6	$ 12
Consumer Portfolio Segment \| Home Equity
Financing Receivable, Modifications
Number of contracts	1	4
Recorded Investment in Loans Modified in a TDR During the Period	$ 0	$ 0
Consumer Portfolio Segment \| Indirect secured consumer loans
Financing Receivable, Modifications
Number of contracts	3
Recorded Investment in Loans Modified in a TDR During the Period	$ 0
Consumer Portfolio Segment \| Credit Card
Financing Receivable, Modifications
Number of contracts	201	283
Recorded Investment in Loans Modified in a TDR During the Period	$ 1	$ 2

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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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