Credit Quality and the Allowance for Loan and Lease Losses - Summary of Loans Modified in a TDR (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020 USD ($) loan	Jun. 30, 2019 USD ($) loan	Jun. 30, 2020 USD ($) loan	Jun. 30, 2019 USD ($) loan
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period \| loan	1,184	1,569	3,340	3,180
Amortized Cost Basis of Loans Modified in a TDR During the Period	$ 174	$ 93	$ 294	$ 158
Increase to ALLL Upon Modification	18	(7)	31	(10)
Charge-offs Recognized Upon Modification	$ 0	$ 6	$ 0	$ 7
Commercial \| Commercial and industrial loans
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period \| loan	33	25	63	38
Amortized Cost Basis of Loans Modified in a TDR During the Period	$ 107	$ 62	$ 176	$ 96
Increase to ALLL Upon Modification	14	(9)	24	(14)
Charge-offs Recognized Upon Modification	$ 0	$ 5	$ 0	$ 5
Commercial \| Commercial mortgage owner-occupied loans
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period \| loan	17	6	28	9
Amortized Cost Basis of Loans Modified in a TDR During the Period	$ 12	$ 5	$ 19	$ 9
Increase to ALLL Upon Modification	0	0	0	0
Charge-offs Recognized Upon Modification	$ 0	$ 0	$ 0	$ 0
Commercial \| Commercial mortgage nonowner-occupied loans
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period \| loan	9		12
Amortized Cost Basis of Loans Modified in a TDR During the Period	$ 14		$ 22
Increase to ALLL Upon Modification	0		0
Charge-offs Recognized Upon Modification	$ 0		$ 0
Commercial \| Commercial construction loans
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period \| loan	2		3
Amortized Cost Basis of Loans Modified in a TDR During the Period	$ 21		$ 21
Increase to ALLL Upon Modification	1		1
Charge-offs Recognized Upon Modification	$ 0		$ 0
Residential Mortgage
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period \| loan	109	139	293	275
Amortized Cost Basis of Loans Modified in a TDR During the Period	$ 13	$ 17	$ 37	$ 35
Increase to ALLL Upon Modification	1	0	1	0
Charge-offs Recognized Upon Modification	$ 0	$ 0	$ 0	$ 0
Consumer \| Home equity
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period \| loan	21	16	42	37
Amortized Cost Basis of Loans Modified in a TDR During the Period	$ 2	$ 1	$ 4	$ 2
Increase to ALLL Upon Modification	0	0	(1)	0
Charge-offs Recognized Upon Modification	$ 0	$ 0	$ 0	$ 0
Consumer \| Indirect secured consumer loans
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period \| loan	20	9	42	38
Amortized Cost Basis of Loans Modified in a TDR During the Period	$ 0	$ 0	$ 0	$ 0
Increase to ALLL Upon Modification	0	0	0	0
Charge-offs Recognized Upon Modification	$ 0	$ 0	$ 0	$ 0
Consumer \| Credit card
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period \| loan	973	1,374	2,857	2,783
Amortized Cost Basis of Loans Modified in a TDR During the Period	$ 5	$ 8	$ 15	$ 16
Increase to ALLL Upon Modification	2	2	6	4
Charge-offs Recognized Upon Modification	$ 0	$ 1	$ 0	$ 2

Amount of credit loss expense (reversal of expense) for financing receivable from change in methodology.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 11
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919244-210447

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
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