Credit Quality (Summary of Loans Modified in a TDR) (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)		Mar. 31, 2018 USD ($)
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period	1,611		2,271
Recorded Investment in Loans Modified in a TDR During the Period	$ 65		$ 117
Increase (Decrease) to ALLL Upon Modification	(3)		16
Charge-offs Recognized Upon Modification	$ 1		$ 0
Commercial Portfolio Segment | Commercial and Industrial Loans
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period	13	[1],[2]	12	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period	$ 34	[2]	$ 72	[4]
Increase (Decrease) to ALLL Upon Modification	(5)	[2]	13	[4]
Charge-offs Recognized Upon Modification	$ 0	[2]	$ 0	[4]
Commercial Portfolio Segment | Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period	3	[1],[2]	2	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period	$ 4	[2]	$ 0	[4]
Increase (Decrease) to ALLL Upon Modification	0	[2]	0	[4]
Charge-offs Recognized Upon Modification	$ 0	[2]	$ 0	[4]
Residential Mortgage Loans
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period	136		247
Recorded Investment in Loans Modified in a TDR During the Period	$ 18		$ 33
Increase (Decrease) to ALLL Upon Modification	0		1
Charge-offs Recognized Upon Modification	$ 0		$ 0
Consumer Portfolio Segment | Home Equity
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period	21	[1],[2]	25	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period	$ 1	[2]	$ 2	[4]
Increase (Decrease) to ALLL Upon Modification	0	[2]	0	[4]
Charge-offs Recognized Upon Modification	$ 0	[2]	$ 0	[4]
Consumer Portfolio Segment | Indirect secured consumer loans
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period	29	[1],[2]	20	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period	$ 0	[2]	$ 0	[4]
Increase (Decrease) to ALLL Upon Modification	0	[2]	0	[4]
Charge-offs Recognized Upon Modification	$ 0	[2]	$ 0	[4]
Consumer Portfolio Segment | Credit Card
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period	1,409	[1],[2]	1,965	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period	$ 8	[2]	$ 10	[4]
Increase (Decrease) to ALLL Upon Modification	2	[2]	2	[4]
Charge-offs Recognized Upon Modification	$ 1	[2]	$ 0	[4]

[1] Represents number of loans post-modification and excludes loans previously modified in a TDR .

[2] Excludes all loans and leases held for sale and loans acquired with deteriorated credit quality which were accounted for within a pool .

[3] Represents number of loans post-modification and excludes loans previously modified in a TDR .

[4] Excludes all loans and leases held for sale and loans acquired with deteriorated credit quality which were accounted for within a pool .