Credit Quality and the Allowance for Loan and Lease Losses - Summary of Subsequent Defaults (Details) $ in Millions	12 Months Ended
Dec. 31, 2021 USD ($) contract	Dec. 31, 2020 USD ($) contract	Dec. 31, 2019 USD ($) contract
Financing Receivable, Modifications
Number of Contracts \| contract	467	457	961
Amortized Cost \| $	$ 41	$ 43	$ 66
Commercial \| Commercial and industrial loans
Financing Receivable, Modifications
Number of Contracts \| contract	7	13	12
Amortized Cost \| $	$ 1	$ 5	$ 20
Commercial \| Commercial mortgage owner-occupied loans
Financing Receivable, Modifications
Number of Contracts \| contract	3	8	4
Amortized Cost \| $	$ 1	$ 3	$ 1
Commercial \| Commercial mortgage nonowner-occupied loans
Financing Receivable, Modifications
Number of Contracts \| contract	2	3	1
Amortized Cost \| $	$ 25	$ 11	$ 0
Residential Mortgage
Financing Receivable, Modifications
Number of Contracts \| contract	82	149	274
Amortized Cost \| $	$ 10	$ 23	$ 42
Consumer \| Home equity
Financing Receivable, Modifications
Number of Contracts \| contract	28	6	15
Amortized Cost \| $	$ 1	$ 0	$ 0
Consumer \| Indirect secured consumer loans
Financing Receivable, Modifications
Number of Contracts \| contract	130	18
Amortized Cost \| $	$ 2	$ 0
Consumer \| Credit card
Financing Receivable, Modifications
Number of Contracts \| contract	215	260	655
Amortized Cost \| $	$ 1	$ 1	$ 3

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+ 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=123577603&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=123577603&loc=SL6953682-111524

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