Credit Quality and the Allowance for Loan and Lease Losses - Summary of Subsequent Defaults (Details) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020 USD ($) contract	Sep. 30, 2019 USD ($) contract	Sep. 30, 2020 USD ($) contract	Sep. 30, 2019 USD ($) contract
Financing Receivable, Modifications
Number of Contracts \| contract	80	146	393	825
Amortized Cost \| $	$ 10	$ 13	$ 36	$ 54
Commercial \| Commercial and industrial loans
Financing Receivable, Modifications
Number of Contracts \| contract	6	1	12	8
Amortized Cost \| $	$ 1	$ 3	$ 5	$ 20
Commercial \| Commercial mortgage owner-occupied loans
Financing Receivable, Modifications
Number of Contracts \| contract	1	2	8	4
Amortized Cost \| $	$ 1	$ 0	$ 3	$ 1
Commercial \| Commercial mortgage nonowner-occupied loans
Financing Receivable, Modifications
Number of Contracts \| contract			2
Amortized Cost \| $			$ 9
Residential Mortgage
Financing Receivable, Modifications
Number of Contracts \| contract	45	67	117	196
Amortized Cost \| $	$ 8	$ 10	$ 18	$ 30
Consumer \| Home equity
Financing Receivable, Modifications
Number of Contracts \| contract	2	7	5	12
Amortized Cost \| $	$ 0	$ 0	$ 0	$ 0
Consumer \| Indirect secured consumer loans
Financing Receivable, Modifications
Number of Contracts \| contract	6		12
Amortized Cost \| $	$ 0		$ 0
Consumer \| Credit card
Financing Receivable, Modifications
Number of Contracts \| contract	20	69	237	605
Amortized Cost \| $	$ 0	$ 0	$ 1	$ 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=121611835&loc=SL6953682-111524

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+ 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=121611835&loc=SL6953682-111524

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