Asset Quality - Financing Receivable Credit Quality Indicators (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 90,178	$ 89,552
Consumer Portfolio Segment, PCI [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	320	334
Consumer Portfolio Segment, PCI [Member] | Residential Prime Financing Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	317	331
Consumer Portfolio Segment, PCI [Member] | Consumer Direct Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3	3
Consumer Portfolio Segment, PCI [Member] | Consumer Credit Card [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer Portfolio Segment, PCI [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer Portfolio Segment Excluding PCI [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	23,113	22,908
Consumer Portfolio Segment Excluding PCI [Member] | Residential Prime Financing Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	16,144	16,324
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Direct Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,162	1,806
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Credit Card [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,086	1,144
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,721	3,634
Commercial Portfolio Segment Excluding PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	66,514	66,069
Commercial Portfolio Segment Excluding PCI Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	64,253	63,904
Commercial Portfolio Segment Excluding PCI Loans [Member] | Criticized (Accruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,997	1,922
Commercial Portfolio Segment Excluding PCI Loans [Member] | Criticized (Nonaccruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	264	243
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	46,416	45,692
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial and Industrial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	44,691	44,138
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial and Industrial [Member] | Criticized (Accruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,555	1,402
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial and Industrial [Member] | Criticized (Nonaccruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	170	152
Commercial Portfolio Segment Excluding PCI Loans [Member] | RE Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	14,172	14,107
Commercial Portfolio Segment Excluding PCI Loans [Member] | RE Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	13,734	13,672
Commercial Portfolio Segment Excluding PCI Loans [Member] | RE Commercial [Member] | Criticized (Accruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	355	354
Commercial Portfolio Segment Excluding PCI Loans [Member] | RE Commercial [Member] | Criticized (Nonaccruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	83	81
Commercial Portfolio Segment Excluding PCI Loans [Member] | RE Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,419	1,664
Commercial Portfolio Segment Excluding PCI Loans [Member] | RE Construction [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,362	1,537
Commercial Portfolio Segment Excluding PCI Loans [Member] | RE Construction [Member] | Criticized (Accruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	55	125
Commercial Portfolio Segment Excluding PCI Loans [Member] | RE Construction [Member] | Criticized (Nonaccruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2	2
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,507	4,606
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial Leases [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,466	4,557
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial Leases [Member] | Criticized (Accruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	32	41
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial Leases [Member] | Criticized (Nonaccruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	9	8
Commercial Portfolio Segment, PCI [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	231	241
Commercial Portfolio Segment, PCI [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	162	164
Commercial Portfolio Segment, PCI [Member] | Criticized (Accruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	69	77
Commercial Portfolio Segment, PCI [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	58	61
Commercial Portfolio Segment, PCI [Member] | Commercial and Industrial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	36	37
Commercial Portfolio Segment, PCI [Member] | Commercial and Industrial [Member] | Criticized (Accruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	22	24
Commercial Portfolio Segment, PCI [Member] | RE Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	172	178
Commercial Portfolio Segment, PCI [Member] | RE Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	125	125
Commercial Portfolio Segment, PCI [Member] | RE Commercial [Member] | Criticized (Accruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	47	53
Commercial Portfolio Segment, PCI [Member] | RE Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1	2
Commercial Portfolio Segment, PCI [Member] | RE Construction [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1	2
Commercial Portfolio Segment, PCI [Member] | RE Construction [Member] | Criticized (Accruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial Portfolio Segment, PCI [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial Portfolio Segment, PCI [Member] | Commercial Leases [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial Portfolio Segment, PCI [Member] | Commercial Leases [Member] | Criticized (Accruing) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
FICO Score, 750 and Above [Member] | Consumer Portfolio Segment, PCI [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	126	137
FICO Score, 750 and Above [Member] | Consumer Portfolio Segment, PCI [Member] | Residential Prime Financing Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	126	137
FICO Score, 750 and Above [Member] | Consumer Portfolio Segment, PCI [Member] | Consumer Direct Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
FICO Score, 750 and Above [Member] | Consumer Portfolio Segment, PCI [Member] | Consumer Credit Card [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
FICO Score, 750 and Above [Member] | Consumer Portfolio Segment, PCI [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
FICO Score, 750 and Above [Member] | Consumer Portfolio Segment Excluding PCI [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	12,522	12,511
FICO Score, 750 and Above [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Residential Prime Financing Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	9,818	9,794
FICO Score, 750 and Above [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Consumer Direct Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	548	549
FICO Score, 750 and Above [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Consumer Credit Card [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	477	521
FICO Score, 750 and Above [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,679	1,647
FICO Score, 660 to 749 [Member] | Consumer Portfolio Segment, PCI [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	96	96
FICO Score, 660 to 749 [Member] | Consumer Portfolio Segment, PCI [Member] | Residential Prime Financing Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	95	95
FICO Score, 660 to 749 [Member] | Consumer Portfolio Segment, PCI [Member] | Consumer Direct Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1	1
FICO Score, 660 to 749 [Member] | Consumer Portfolio Segment, PCI [Member] | Consumer Credit Card [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
FICO Score, 660 to 749 [Member] | Consumer Portfolio Segment, PCI [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
FICO Score, 660 to 749 [Member] | Consumer Portfolio Segment Excluding PCI [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,212	7,433
FICO Score, 660 to 749 [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Residential Prime Financing Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,690	4,906
FICO Score, 660 to 749 [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Consumer Direct Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	683	700
FICO Score, 660 to 749 [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Consumer Credit Card [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	485	507
FICO Score, 660 to 749 [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,354	1,320
FICO Score, Less than 660 [Member] | Consumer Portfolio Segment, PCI [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	92	99
FICO Score, Less than 660 [Member] | Consumer Portfolio Segment, PCI [Member] | Residential Prime Financing Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	90	97
FICO Score, Less than 660 [Member] | Consumer Portfolio Segment, PCI [Member] | Consumer Direct Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2	2
FICO Score, Less than 660 [Member] | Consumer Portfolio Segment, PCI [Member] | Consumer Credit Card [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
FICO Score, Less than 660 [Member] | Consumer Portfolio Segment, PCI [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
FICO Score, Less than 660 [Member] | Consumer Portfolio Segment Excluding PCI [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,291	2,316
FICO Score, Less than 660 [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Residential Prime Financing Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,394	1,411
FICO Score, Less than 660 [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Consumer Direct Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	217	224
FICO Score, Less than 660 [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Consumer Credit Card [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	124	116
FICO Score, Less than 660 [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	556	565
FICO Score, No Score [Member] | Consumer Portfolio Segment, PCI [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6	2
FICO Score, No Score [Member] | Consumer Portfolio Segment, PCI [Member] | Residential Prime Financing Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6	2
FICO Score, No Score [Member] | Consumer Portfolio Segment, PCI [Member] | Consumer Direct Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
FICO Score, No Score [Member] | Consumer Portfolio Segment, PCI [Member] | Consumer Credit Card [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
FICO Score, No Score [Member] | Consumer Portfolio Segment, PCI [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
FICO Score, No Score [Member] | Consumer Portfolio Segment Excluding PCI [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,088	648
FICO Score, No Score [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Residential Prime Financing Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	242	213
FICO Score, No Score [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Consumer Direct Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	714	333
FICO Score, No Score [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Consumer Credit Card [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
FICO Score, No Score [Member] | Consumer Portfolio Segment Excluding PCI [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 132	$ 102