Summary of Loans Modified in a TDR (Detail) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2015 USD ($)		Sep. 30, 2014 USD ($)		Sep. 30, 2015 USD ($)		Sep. 30, 2014 USD ($)
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period						11,227	[1],[2]	6,916	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period						$ 314	[1]	$ 387	[3]
Increase (Decrease) to ALLL Upon Modification						21	[1]	$ 22	[3]
Charge-offs Recognized Upon Modification	[1]					$ 8
Quarterly
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		3,551	[5],[6]	2,218	[7],[8]
Recorded Investment in Loans Modified in a TDR During the Period		$ 82	[5]	$ 95	[7]
Increase (Decrease) to ALLL Upon Modification		13	[5]	$ 13	[7]
Charge-offs Recognized Upon Modification	[5]	$ 2
Commercial Portfolio Segment | Commercial and Industrial Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period						63	[1],[2]	83	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period						$ 105	[1]	$ 154	[3]
Increase (Decrease) to ALLL Upon Modification						7	[1]	$ 12	[3]
Charge-offs Recognized Upon Modification	[1]					$ 3
Commercial Portfolio Segment | Commercial and Industrial Loans | Quarterly
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		15	[5],[6]	17	[7],[8]
Recorded Investment in Loans Modified in a TDR During the Period		$ 17	[5]	$ 35	[7]
Increase (Decrease) to ALLL Upon Modification		$ 7	[5]	$ 10	[7]
Commercial Portfolio Segment | Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period						14	[1],[2]	25	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period						$ 15	[1]	$ 53	[3]
Increase (Decrease) to ALLL Upon Modification						$ (2)	[1]	$ (1)	[3]
Commercial Portfolio Segment | Commercial Mortgage Loans, Owner-occupied | Quarterly
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		1	[5],[6]	5	[7],[8]
Recorded Investment in Loans Modified in a TDR During the Period	[7]			$ 2
Commercial Portfolio Segment | Commercial Mortgage Loans, Nonowner-Occupied
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period						11	[1],[2]	19	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period						$ 7	[1]	$ 11	[3]
Increase (Decrease) to ALLL Upon Modification	[3]							$ (2)
Commercial Portfolio Segment | Commercial Mortgage Loans, Nonowner-Occupied | Quarterly
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	[7],[8]			8
Recorded Investment in Loans Modified in a TDR During the Period	[7]			$ 4
Increase (Decrease) to ALLL Upon Modification	[3]			$ (1)
Residential Mortgage Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period						855	[1],[2]	812	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period						$ 121	[1]	$ 119	[3]
Increase (Decrease) to ALLL Upon Modification						$ 7	[1]	$ 7	[3]
Residential Mortgage Loans | Quarterly
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		301	[5],[6]	240	[7],[8]
Recorded Investment in Loans Modified in a TDR During the Period		$ 44	[5]	$ 35	[7]
Increase (Decrease) to ALLL Upon Modification		$ 3	[5]	$ 2	[7]
Consumer Portfolio Segment | Home Equity
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period						203	[1],[2]	212	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period						$ 11	[1]	$ 9	[3]
Increase (Decrease) to ALLL Upon Modification	[1]					$ (1)
Consumer Portfolio Segment | Home Equity | Quarterly
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		60	[5],[6]	106	[7],[8]
Recorded Investment in Loans Modified in a TDR During the Period		$ 4	[5]	$ 5	[7]
Consumer Portfolio Segment | Automobile Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period						357	[1],[2]	431	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period						$ 6	[1]	$ 7	[3]
Consumer Portfolio Segment | Automobile Loans | Quarterly
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		98	[5],[6]	172	[7],[8]
Recorded Investment in Loans Modified in a TDR During the Period		$ 2	[5]	$ 3	[7]
Consumer Portfolio Segment | Credit Card
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period						9,724	[1],[2]	5,334	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period						$ 49	[1]	$ 34	[3]
Increase (Decrease) to ALLL Upon Modification						10	[1]	$ 6	[3]
Charge-offs Recognized Upon Modification	[1]					$ 5
Consumer Portfolio Segment | Credit Card | Quarterly
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period		3,076	[5],[6]	1,670	[7],[8]
Recorded Investment in Loans Modified in a TDR During the Period		$ 15	[5]	$ 11	[7]
Increase (Decrease) to ALLL Upon Modification		3	[5]	$ 2	[7]
Charge-offs Recognized Upon Modification	[5]	$ 2

[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.

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

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

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

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