Credit Quality and the Allowance for Loan and Lease Losses - Summary of Subsequent Defaults (Details) $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($) contract	Mar. 31, 2020 USD ($) contract
Financing Receivable, Modifications
Number of Contracts \| contract	97	255
Amortized Cost \| $	$ 31	$ 13
Commercial \| Commercial mortgage owner-occupied loans
Financing Receivable, Modifications
Number of Contracts \| contract		2
Amortized Cost \| $		$ 1
Commercial \| Commercial mortgage nonowner-occupied loans
Financing Receivable, Modifications
Number of Contracts \| contract	1	1
Amortized Cost \| $	$ 25	$ 5
Residential Mortgage
Financing Receivable, Modifications
Number of Contracts \| contract	35	47
Amortized Cost \| $	$ 4	$ 6
Consumer \| Home equity
Financing Receivable, Modifications
Number of Contracts \| contract	12	1
Amortized Cost \| $	$ 1	$ 0
Consumer \| Indirect secured consumer loans
Financing Receivable, Modifications
Number of Contracts \| contract	26	3
Amortized Cost \| $	$ 1	$ 0
Consumer \| Credit card
Financing Receivable, Modifications
Number of Contracts \| contract	23	201
Amortized Cost \| $	$ 0	$ 1

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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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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=121611835&loc=SL6953682-111524

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