Summary of Loans Modified in a TDR (Detail) (Quarterly, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	4,208	[1],[2]	2,457	[1],[2]
Recorded Investment in Loans Modified in a TDR During the Period	$ 96	[1]	$ 97	[1]
Increase (Decrease) to ALLL Upon Modification	(3)	[1]	(1)	[1]
Charge-offs Recognized Upon Modification	3	[1]
Commercial Portfolio Segment | Commercial and Industrial Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	21	[1],[2]	22	[1],[2]
Recorded Investment in Loans Modified in a TDR During the Period	18	[1]	19	[1]
Increase (Decrease) to ALLL Upon Modification	(7)	[1]	(4)	[1]
Charge-offs Recognized Upon Modification	3	[1]
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]	16	[1],[2]
Recorded Investment in Loans Modified in a TDR During the Period	8	[1]	12	[1]
Increase (Decrease) to ALLL Upon Modification	(1)	[1]	(1)	[1]
Commercial Portfolio Segment | Commercial Mortgage Loans, Nonowner-Occupied
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	6	[1],[2]	7	[1],[2]
Recorded Investment in Loans Modified in a TDR During the Period	3	[1]	6	[1]
Increase (Decrease) to ALLL Upon Modification			(1)	[1]
Residential Mortgage Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	300	[1],[2]	310	[1],[2]
Recorded Investment in Loans Modified in a TDR During the Period	42	[1]	45	[1]
Increase (Decrease) to ALLL Upon Modification	1	[1]	3	[1]
Consumer Portfolio Segment | Home Equity
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	76	[1],[2]	35	[1],[2]
Recorded Investment in Loans Modified in a TDR During the Period	4	[1]	1	[1]
Consumer Portfolio Segment | Automobile Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	131	[1],[2]	116	[1],[2]
Recorded Investment in Loans Modified in a TDR During the Period	2	[1]	2	[1]
Consumer Portfolio Segment | Credit Card
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	3,667	[1],[2]	1,951	[1],[2]
Recorded Investment in Loans Modified in a TDR During the Period	19	[1]	12	[1]
Increase (Decrease) to ALLL Upon Modification	$ 4	[1]	$ 2	[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.