Credit Quality - Summary of Loans Modified in a TDR (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	1,569	2,273	3,180	4,544
Recorded Investment in Loans Modified in a TDR During the Period	$ 93	$ 166	$ 158	$ 282
Increase (Decrease) to ALLL Upon Modification	(7)	0	(10)	16
Charge-offs Recognized Upon Modification	$ 6	$ 1	$ 7	$ 1
Commercial Portfolio Segment | Commercial and Industrial Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	25	13	38	25
Recorded Investment in Loans Modified in a TDR During the Period	$ 62	$ 64	$ 96	$ 135
Increase (Decrease) to ALLL Upon Modification	(9)	(4)	(14)	9
Charge-offs Recognized Upon Modification	$ 5	$ 0	$ 5	$ 0
Commercial Portfolio Segment | Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	6		9	2
Recorded Investment in Loans Modified in a TDR During the Period	$ 5		$ 9	$ 0
Increase (Decrease) to ALLL Upon Modification	0		0	0
Charge-offs Recognized Upon Modification	$ 0		$ 0	$ 0
Residential Mortgage Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	139	537	275	784
Recorded Investment in Loans Modified in a TDR During the Period	$ 17	$ 91	$ 35	$ 124
Increase (Decrease) to ALLL Upon Modification	0	2	0	3
Charge-offs Recognized Upon Modification	$ 0	$ 0	$ 0	$ 0
Consumer Portfolio Segment | Home Equity
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	16	29	37	54
Recorded Investment in Loans Modified in a TDR During the Period	$ 1	$ 2	$ 2	$ 4
Increase (Decrease) to ALLL Upon Modification	0	0	0	0
Charge-offs Recognized Upon Modification	$ 0	$ 0	$ 0	$ 0
Consumer Portfolio Segment | Indirect secured consumer loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	9	19	38	39
Recorded Investment in Loans Modified in a TDR During the Period	$ 0	$ 0	$ 0	$ 0
Increase (Decrease) to ALLL Upon Modification	0	0	0	0
Charge-offs Recognized Upon Modification	$ 0	$ 0	$ 0	$ 0
Consumer Portfolio Segment | Credit Card
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	1,374	1,675	2,783	3,640
Recorded Investment in Loans Modified in a TDR During the Period	$ 8	$ 9	$ 16	$ 19
Increase (Decrease) to ALLL Upon Modification	2	2	4	4
Charge-offs Recognized Upon Modification	$ 1	$ 1	$ 2	$ 1