Loans and ACL - Risk Rating (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable
Loans and leases	$ 319,229	$ 299,842
2020	17,089
2019	65,130
2018	41,661
2017	27,442
2016	20,067
Prior	55,494
Revolving Credit	90,783
Loans Converted to Term	2,017
Other (1)	(454)
Credit card
Financing Receivable
Loans and leases	5,300
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Credit	5,268
Loans Converted to Term	35
Other (1)	(3)
Commercial: | Commercial & Industrial
Financing Receivable
Loans and leases	149,161	130,180
2020	7,515
2019	25,809
2018	15,917
2017	10,023
2016	6,876
Prior	15,386
Revolving Credit	68,453
Loans Converted to Term	13
Other (1)	(831)
Commercial: | Commercial & Industrial | Pass
Financing Receivable
Loans and leases	145,212	127,229
2020	7,366
2019	25,371
2018	15,536
2017	9,849
2016	6,598
Prior	14,904
Revolving Credit	66,420
Loans Converted to Term	11
Other (1)	(843)
Commercial: | Commercial & Industrial | Special mention
Financing Receivable
Loans and leases	1,744	1,264
2020	93
2019	170
2018	161
2017	66
2016	143
Prior	101
Revolving Credit	1,010
Loans Converted to Term	0
Other (1)	0
Commercial: | Commercial & Industrial | Substandard
Financing Receivable
Loans and leases	1,762	1,475
2020	53
2019	216
2018	126
2017	74
2016	87
Prior	296
Revolving Credit	926
Loans Converted to Term	1
Other (1)	(17)
Commercial: | Commercial & Industrial | Nonperforming
Financing Receivable
Loans and leases	443	212
2020	3
2019	52
2018	94
2017	34
2016	48
Prior	85
Revolving Credit	97
Loans Converted to Term	1
Other (1)	29
Commercial: | CRE
Financing Receivable
Loans and leases	27,532	26,832
2020	2,031
2019	8,392
2018	6,295
2017	3,533
2016	2,356
Prior	4,303
Revolving Credit	714
Loans Converted to Term	0
Other (1)	(92)
Commercial: | CRE | Pass
Financing Receivable
Loans and leases	26,859	26,393
2020	2,013
2019	8,252
2018	6,166
2017	3,479
2016	2,262
Prior	4,066
Revolving Credit	713
Loans Converted to Term	0
Other (1)	(92)
Commercial: | CRE | Special mention
Financing Receivable
Loans and leases	339	145
2020	1
2019	44
2018	102
2017	12
2016	65
Prior	115
Revolving Credit	0
Loans Converted to Term	0
Other (1)	0
Commercial: | CRE | Substandard
Financing Receivable
Loans and leases	316	284
2020	17
2019	94
2018	23
2017	39
2016	29
Prior	114
Revolving Credit	0
Loans Converted to Term	0
Other (1)	0
Commercial: | CRE | Nonperforming
Financing Receivable
Loans and leases	18	10
2020	0
2019	2
2018	4
2017	3
2016	0
Prior	8
Revolving Credit	1
Loans Converted to Term	0
Other (1)	0
Commercial: | Commercial construction
Financing Receivable
Loans and leases	6,630	6,205
2020	345
2019	1,932
2018	2,236
2017	802
2016	193
Prior	385
Revolving Credit	732
Loans Converted to Term	1
Other (1)	4
Commercial: | Commercial construction | Pass
Financing Receivable
Loans and leases	6,440	6,037
2020	342
2019	1,921
2018	2,164
2017	745
2016	153
Prior	381
Revolving Credit	729
Loans Converted to Term	1
Other (1)	4
Commercial: | Commercial construction | Special mention
Financing Receivable
Loans and leases	42	37
2020	0
2019	5
2018	37
2017	0
2016	0
Prior	0
Revolving Credit	0
Loans Converted to Term	0
Other (1)	0
Commercial: | Commercial construction | Substandard
Financing Receivable
Loans and leases	146	131
2020	3
2019	5
2018	35
2017	56
2016	40
Prior	4
Revolving Credit	3
Loans Converted to Term	0
Other (1)	0
Commercial: | Commercial construction | Nonperforming
Financing Receivable
Loans and leases	2	0
2020	0
2019	1
2018	0
2017	1
2016	0
Prior	0
Revolving Credit	0
Loans Converted to Term	0
Other (1)	0
Commercial: | Lease Financing
Financing Receivable
Loans and leases	5,984	6,122
2020	255
2019	1,875
2018	1,158
2017	1,089
2016	388
Prior	1,263
Revolving Credit	0
Loans Converted to Term	0
Other (1)	(44)
Commercial: | Lease Financing | Pass
Financing Receivable
Loans and leases	5,887	6,039
2020	255
2019	1,864
2018	1,154
2017	1,056
2016	381
Prior	1,221
Revolving Credit	0
Loans Converted to Term	0
Other (1)	(44)
Commercial: | Lease Financing | Special mention
Financing Receivable
Loans and leases	17	19
2020	0
2019	8
2018	3
2017	3
2016	3
Prior	0
Revolving Credit	0
Loans Converted to Term	0
Other (1)	0
Commercial: | Lease Financing | Substandard
Financing Receivable
Loans and leases	53	56
2020	0
2019	3
2018	0
2017	15
2016	2
Prior	33
Revolving Credit	0
Loans Converted to Term	0
Other (1)	0
Commercial: | Lease Financing | Nonperforming
Financing Receivable
Loans and leases	27	8
2020	0
2019	0
2018	1
2017	15
2016	2
Prior	9
Revolving Credit	0
Loans Converted to Term	0
Other (1)	0
Consumer: | Residential Mortgage
Financing Receivable
Loans and leases	53,096	52,071
2020	1,800
2019	8,484
2018	5,603
2017	6,175
2016	6,993
Prior	23,808
Revolving Credit	0
Loans Converted to Term	0
Other (1)	233
Consumer: | Residential Mortgage | Performing
Financing Receivable
Loans and leases	52,848	52,016
2020	1,800
2019	8,480
2018	5,595
2017	6,168
2016	6,985
Prior	23,587
Revolving Credit	0
Loans Converted to Term	0
Other (1)	233
Consumer: | Residential Mortgage | Nonperforming
Financing Receivable
Loans and leases	248	55
2020	0
2019	4
2018	8
2017	7
2016	8
Prior	221
Revolving Credit	0
Loans Converted to Term	0
Other (1)	0
Consumer: | Residential home equity and direct
Financing Receivable
Loans and leases	27,629	27,044
2020	1,296
2019	4,440
2018	2,168
2017	835
2016	421
Prior	797
Revolving Credit	15,616
Loans Converted to Term	1,968
Other (1)	88
Consumer: | Residential home equity and direct | Performing
Financing Receivable
Loans and leases	27,459	26,977
2020	1,296
2019	4,436
2018	2,164
2017	834
2016	420
Prior	789
Revolving Credit	15,553
Loans Converted to Term	1,874
Other (1)	93
Consumer: | Residential home equity and direct | Nonperforming
Financing Receivable
Loans and leases	170	67
2020	0
2019	4
2018	4
2017	1
2016	1
Prior	8
Revolving Credit	63
Loans Converted to Term	94
Other (1)	(5)
Consumer: | Indirect auto
Financing Receivable
Loans and leases	25,146	24,442
2020	2,799
2019	9,757
2018	5,587
2017	3,600
2016	2,089
Prior	1,185
Revolving Credit	0
Loans Converted to Term	0
Other (1)	129
Consumer: | Indirect auto | Performing
Financing Receivable
Loans and leases	25,021	24,342
2020	2,799
2019	9,725
2018	5,548
2017	3,571
2016	2,070
Prior	1,166
Revolving Credit	0
Loans Converted to Term	0
Other (1)	142
Consumer: | Indirect auto | Nonperforming
Financing Receivable
Loans and leases	125	100
2020	0
2019	32
2018	39
2017	29
2016	19
Prior	19
Revolving Credit	0
Loans Converted to Term	0
Other (1)	(13)
Consumer: | Indirect Other
Financing Receivable
Loans and leases	10,980	11,100
2020	1,027
2019	4,319
2018	2,587
2017	1,294
2016	676
Prior	1,010
Revolving Credit	0
Loans Converted to Term	0
Other (1)	67
Consumer: | Indirect Other | Performing
Financing Receivable
Loans and leases	10,979	11,098
2020	1,027
2019	4,319
2018	2,587
2017	1,294
2016	676
Prior	1,009
Revolving Credit	0
Loans Converted to Term	0
Other (1)	67
Consumer: | Indirect Other | Nonperforming
Financing Receivable
Loans and leases	1	2
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	1
Revolving Credit	0
Loans Converted to Term	0
Other (1)	0
Consumer: | Student
Financing Receivable
Loans and leases	7,771	$ 6,743
2020	21
2019	122
2018	110
2017	91
2016	75
Prior	7,357
Revolving Credit	0
Loans Converted to Term	0
Other (1)	(5)
Consumer: | Student | Performing
Financing Receivable
Loans and leases	7,771
2020	21
2019	122
2018	110
2017	91
2016	75
Prior	7,357
Revolving Credit	0
Loans Converted to Term	0
Other (1)	(5)
Consumer: | Student | Nonperforming
Financing Receivable
Loans and leases	0
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Credit	0
Loans Converted to Term	0
Other (1)	$ 0