Summary of Loans Modified in a TDR (Detail) - Quarterly $ in Millions		3 Months Ended
		Mar. 31, 2016 USD ($)		Mar. 31, 2015 USD ($)
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		3,010	[1],[2]	4,208	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 116	[1]	$ 96	[3]
Increase (Decrease) to ALLL Upon Modification	[3]			(3)
Charge-offs Recognized Upon Modification		$ 1	[1]	$ 3	[3]
Commercial Portfolio Segment | Commercial and Industrial Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		24	[1],[2]	21	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 56	[1]	$ 18	[3]
Increase (Decrease) to ALLL Upon Modification		$ (2)	[1]	(7)	[3]
Charge-offs Recognized Upon Modification	[3]			$ 3
Commercial Portfolio Segment | Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		7	[1],[2]	7	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 6	[1]	$ 8	[3]
Increase (Decrease) to ALLL Upon Modification		$ (2)	[1]	$ (1)	[3]
Commercial Portfolio Segment | Commercial Mortgage Loans, Nonowner-Occupied
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		2	[1],[2]	6	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period	[3]			$ 3
Residential Mortgage Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		243	[1],[2]	300	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 36	[1]	$ 42	[3]
Increase (Decrease) to ALLL Upon Modification		$ 2	[1]	$ 1	[3]
Consumer Portfolio Segment | Home Equity
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		64	[1],[2]	76	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 5	[1]	$ 4	[3]
Consumer Portfolio Segment | Automobile Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		78	[1],[2]	131	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 1	[1]	$ 2	[3]
Consumer Portfolio Segment | Credit Card
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		2,592	[1],[2]	3,667	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 12	[1]	$ 19	[3]
Increase (Decrease) to ALLL Upon Modification		2	[1]	$ 4	[3]
Charge-offs Recognized Upon Modification	[1]	$ 1

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

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

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

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