Credit Quality (Summary of Loans Modified in a TDR) (Detail)		3 Months Ended				6 Months Ended
		Jun. 30, 2016 USD ($)		Jun. 30, 2015 USD ($)		Jun. 30, 2016 USD ($)		Jun. 30, 2015 USD ($)
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period		2,669	[1],[2]	3,468,000,000	[3],[4]	5,679	[1],[2]	7,676	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 119,000,000	[1]	$ 136,000,000	[3]	$ 235,000,000	[1]	$ 232,000,000	[3]
Increase (Decrease) to ALLL Upon Modification		16,000,000	[1]	11,000,000	[3]	16,000,000	[1]	8,000,000	[3]
Charge-offs Recognized Upon Modification		$ 1,000,000	[1]	$ 3,000,000	[3]	$ 2,000,000	[1]	$ 6,000,000	[3]
Commercial Portfolio Segment | Commercial and Industrial Loans
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period		20	[1],[2]	27,000,000	[3],[4]	44	[1],[2]	48	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 61,000,000	[1]	$ 70,000,000	[3]	$ 117,000,000	[1]	$ 88,000,000	[3]
Increase (Decrease) to ALLL Upon Modification		$ 11,000,000	[1]	$ 7,000,000	[3]	$ 9,000,000	[1]
Charge-offs Recognized Upon Modification	[3]							$ 3,000,000
Commercial Portfolio Segment | Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period		3	[1],[2]	6,000,000	[3],[4]	10	[1],[2]	13	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 2,000,000	[1]	$ 7,000,000	[3]	$ 8,000,000	[1]	$ 15,000,000	[3]
Increase (Decrease) to ALLL Upon Modification				$ (1,000,000)	[3]	$ (2,000,000)	[1]	$ (2,000,000)	[3]
Commercial Portfolio Segment | Commercial Mortgage Loans, Nonowner-Occupied
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period		2	[1],[2]	5,000,000	[3],[4]	4	[1],[2]	11	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 5,000,000	[1]	$ 4,000,000	[3]	$ 5,000,000	[1]	$ 7,000,000	[3]
Increase (Decrease) to ALLL Upon Modification	[1]	$ 1,000,000				$ 1,000,000
Residential Mortgage Loans
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period		262	[1],[2]	254,000,000	[3],[4]	505	[1],[2]	554	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 37,000,000	[1]	$ 35,000,000	[3]	$ 73,000,000	[1]	$ 77,000,000	[3]
Increase (Decrease) to ALLL Upon Modification		$ 2,000,000	[1]	$ 3,000,000	[3]	$ 4,000,000	[1]	$ 4,000,000	[3]
Consumer Portfolio Segment | Home Equity
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period		62	[1],[2]	67,000,000	[3],[4]	126	[1],[2]	143	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 2,000,000	[1]	$ 3,000,000	[3]	$ 7,000,000	[1]	$ 7,000,000	[3]
Increase (Decrease) to ALLL Upon Modification	[3]			$ (1,000,000)				$ (1,000,000)
Consumer Portfolio Segment | Automobile Loans
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period		58	[1],[2]	128,000,000	[3],[4]	136	[1],[2]	259	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 1,000,000	[1]	$ 2,000,000	[3]	$ 2,000,000	[1]	$ 4,000,000	[3]
Consumer Portfolio Segment | Credit Card
Financing Receivable, Modifications
Number of Loans Modified in a TDR During the Period		2,262	[1],[2]	2,981,000,000	[3],[4]	4,854	[1],[2]	6,648	[3],[4]
Recorded Investment in Loans Modified in a TDR During the Period		$ 11,000,000	[1]	$ 15,000,000	[3]	$ 23,000,000	[1]	$ 34,000,000	[3]
Increase (Decrease) to ALLL Upon Modification		2,000,000	[1]	3,000,000	[3]	4,000,000	[1]	7,000,000	[3]
Charge-offs Recognized Upon Modification		$ 1,000,000	[1]	$ 3,000,000	[3]	$ 2,000,000	[1]	$ 3,000,000	[3]

[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 .