Credit Quality and the Allowance for Loan and Lease Losses - Summary of Recorded Investment in Portfolio Loans and Leases by Age and Class (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Financing Receivable, Recorded Investment, Past Due
Portfolio loans and leases, net		$ 108,157		$ 108,356
Residential mortgage loans
Financing Receivable, Recorded Investment, Past Due
Residential mortgage loans		174		183
Commercial
Financing Receivable, Recorded Investment, Past Due
Current loans and leases		70,806		69,657
Past due		444		301
Portfolio loans and leases, net		71,250		69,958
90 days past due and still accruing		32		26
Commercial | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due		218		154
Commercial | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due		226		147
Commercial | Commercial and industrial loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases		51,413		50,305
Past due		282		237
Portfolio loans and leases, net		51,695		50,542
90 days past due and still accruing		4		11
Commercial | Commercial and industrial loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due		140		133
Commercial | Commercial and industrial loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due		142		104
Commercial | Commercial mortgage owner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases		4,753		4,853
Past due		51		27
Portfolio loans and leases, net		4,804		4,880
90 days past due and still accruing		22		9
Commercial | Commercial mortgage owner-occupied loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due		14		4
Commercial | Commercial mortgage owner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due		37		23
Commercial | Commercial mortgage nonowner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases		5,979		6,072
Past due		95		11
Portfolio loans and leases, net		6,074		6,083
90 days past due and still accruing		4		6
Commercial | Commercial mortgage nonowner-occupied loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due		58		5
Commercial | Commercial mortgage nonowner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due		37		6
Commercial | Commercial construction loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases		5,654		5,089
Past due		2		1
Portfolio loans and leases, net		5,656		5,090
90 days past due and still accruing		0		0
Commercial | Commercial construction loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due		2		1
Commercial | Commercial construction loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due		0		0
Commercial | Commercial leases
Financing Receivable, Recorded Investment, Past Due
Current loans and leases		3,007		3,338
Past due		14		25
Portfolio loans and leases, net		3,021		3,363
90 days past due and still accruing		2		0
Commercial | Commercial leases | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due		4		11
Commercial | Commercial leases | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due		10		14
Residential Mortgage
Financing Receivable, Recorded Investment, Past Due
Residential mortgage loans		174		183
Residential Mortgage | Federal Housing Administration Loan
Financing Receivable, Recorded Investment, Past Due
Losses due to claim denials and curtailments	$ 1	2	$ 1
Residential Mortgage | 30-89 Days | Federal Housing Administration Loan
Financing Receivable, Recorded Investment, Past Due
Past due		91		94
Residential Mortgage | 90 Days or More | Federal Housing Administration Loan
Financing Receivable, Recorded Investment, Past Due
Past due		$ 249		261
Residential Mortgage | Residential mortgage loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases				16,372
Past due				169
Portfolio loans and leases, net				16,541
90 days past due and still accruing				50
Residential Mortgage | Residential mortgage loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due				27
Residential Mortgage | Residential mortgage loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due				142
Consumer | Home equity
Financing Receivable, Recorded Investment, Past Due
Current loans and leases				5,965
Past due				118
Portfolio loans and leases, net				6,083
90 days past due and still accruing				1
Consumer | Home equity | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due				61
Consumer | Home equity | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due				57
Consumer | Indirect secured consumer loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases				11,389
Past due				149
Portfolio loans and leases, net				11,538
90 days past due and still accruing				10
Consumer | Indirect secured consumer loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due				132
Consumer | Indirect secured consumer loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due				17
Consumer | Credit card
Financing Receivable, Recorded Investment, Past Due
Current loans and leases				2,434
Past due				98
Portfolio loans and leases, net				2,532
90 days past due and still accruing				42
Consumer | Credit card | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due				50
Consumer | Credit card | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due				48
Consumer | Other consumer loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases				2,702
Past due				21
Portfolio loans and leases, net				2,723
90 days past due and still accruing				1
Consumer | Other consumer loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due				18
Consumer | Other consumer loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due				3
Residential Mortgage and Consumer
Financing Receivable, Recorded Investment, Past Due
Current loans and leases				38,862
Past due				555
Portfolio loans and leases, net				39,417
90 days past due and still accruing				104
Residential Mortgage and Consumer | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due				288
Residential Mortgage and Consumer | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due				$ 267