Summary of Loans Modified in a TDR (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended						9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Quarterly [Member]	Sep. 30, 2011 Quarterly [Member]	Sep. 30, 2012 Commercial Portfolio Segment CommercialAndIndustrialLoansMember [Member]	Sep. 30, 2011 Commercial Portfolio Segment CommercialAndIndustrialLoansMember [Member]	Sep. 30, 2012 Commercial Portfolio Segment CommercialAndIndustrialLoansMember [Member] Quarterly [Member]	Sep. 30, 2011 Commercial Portfolio Segment CommercialAndIndustrialLoansMember [Member] Quarterly [Member]	Sep. 30, 2012 Commercial Portfolio Segment Commercial Mortgage Loans Owner Occupied [Member]	Sep. 30, 2011 Commercial Portfolio Segment Commercial Mortgage Loans Owner Occupied [Member]	Sep. 30, 2012 Commercial Portfolio Segment Commercial Mortgage Loans Owner Occupied [Member] Quarterly [Member]	Sep. 30, 2011 Commercial Portfolio Segment Commercial Mortgage Loans Owner Occupied [Member] Quarterly [Member]	Sep. 30, 2012 Commercial Portfolio Segment Commercial Mortgage Loans Non Owner Occupied [Member]	Sep. 30, 2011 Commercial Portfolio Segment Commercial Mortgage Loans Non Owner Occupied [Member]	Sep. 30, 2012 Commercial Portfolio Segment Commercial Mortgage Loans Non Owner Occupied [Member] Quarterly [Member]	Sep. 30, 2011 Commercial Portfolio Segment Commercial Mortgage Loans Non Owner Occupied [Member] Quarterly [Member]	Sep. 30, 2012 Commercial Portfolio Segment Commercial Construction	Sep. 30, 2011 Commercial Portfolio Segment Commercial Construction	Sep. 30, 2012 Commercial Portfolio Segment Commercial Construction Quarterly [Member]	Sep. 30, 2011 Commercial Portfolio Segment Commercial Construction Quarterly [Member]	Sep. 30, 2011 Commercial Portfolio Segment Commercial Leases [Member]	Sep. 30, 2012 Commercial Portfolio Segment Commercial Leases [Member] Quarterly [Member]	Sep. 30, 2012 Consumer Portfolio Segment Home Equity	Sep. 30, 2011 Consumer Portfolio Segment Home Equity	Sep. 30, 2012 Consumer Portfolio Segment Home Equity Quarterly [Member]	Sep. 30, 2011 Consumer Portfolio Segment Home Equity Quarterly [Member]	Sep. 30, 2012 Consumer Portfolio Segment Automobile Loans	Sep. 30, 2011 Consumer Portfolio Segment Automobile Loans	Sep. 30, 2011 Consumer Portfolio Segment Automobile Loans Quarterly [Member]	Sep. 30, 2012 Consumer Portfolio Segment Automobile Loans Quarterly [Member]	Sep. 30, 2012 Consumer Portfolio Segment Credit Card	Sep. 30, 2011 Consumer Portfolio Segment Credit Card	Sep. 30, 2012 Consumer Portfolio Segment Credit Card Quarterly [Member]	Sep. 30, 2011 Consumer Portfolio Segment Credit Card Quarterly [Member]	Sep. 30, 2012 Residential Mortgage Loans	Sep. 30, 2011 Residential Mortgage Loans	Sep. 30, 2012 Residential Mortgage Loans Quarterly [Member]	Sep. 30, 2011 Residential Mortgage Loans Quarterly [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	11,498	12,684	3,370	3,916	61	35	20	7	52	15	16	7	52	28	12	15	14	9	3	4	2	6	1,034	999	364	347	774	1,135	371	213	7,963	9,188	2,231	2,781	1,542	1,273	505	384
Recorded Investment in Loans Modified in a TDR During the Period	$ 592	$ 651	$ 190	$ 228	$ 45	$ 113	$ 20	$ 33	$ 45	$ 20	$ 29	$ 5	$ 78	$ 77	$ 11	$ 44	$ 36	$ 43		$ 22		$ 3	$ 63	$ 61	$ 21	$ 21	$ 12	$ 21	$ 7	$ 3	$ 51	$ 61	$ 13	$ 17	$ 259	$ 255	$ 90	$ 79
Increase (Decrease) to ALLL Upon Modification	6	13	4	2	(10)	2		(2)	(6)	(6)	(3)	(4)	(8)	(17)	(3)	(4)	(4)	(4)					3	1	1	1	2	2	1		7	9	2	2	22	26	7	8
Charge-offs Recognized Upon Modification	$ 7	$ 11	$ 7		$ 5	$ 1	$ 5		$ 2	$ 7	$ 2			$ 3