Summary of Average Impaired Loans and Leases and Interest Income by Class (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Average Recorded Investment	$ 3,012	$ 2,980	$ 3,005	$ 2,963
Interest Income Recognized	32	55	56	103
Commercial Portfolio Segment | Commercial And Industrial Loans [Member]
Average Recorded Investment	467	521	481	495
Interest Income Recognized	1	12	2	25
Commercial Portfolio Segment | Commercial Mortgage Loans Owner Occupied [Member]
Average Recorded Investment	164	121	152	126
Interest Income Recognized	1	5	2	10
Commercial Portfolio Segment | Commercial Mortgage Loans Non Owner Occupied [Member]
Average Recorded Investment	361	280	341	290
Interest Income Recognized	2	8	4	16
Commercial Portfolio Segment | Commercial Construction
Average Recorded Investment	177	197	190	183
Interest Income Recognized	1	6	2	11
Commercial Portfolio Segment | Commercial Leases [Member]
Average Recorded Investment	10	19	11	23
Residential Mortgage Loans
Average Recorded Investment	1,270	1,222	1,266	1,209
Interest Income Recognized	13	11	25	21
Consumer Portfolio Segment | Home Equity
Average Recorded Investment	438	440	441	444
Interest Income Recognized	12	11	18	17
Consumer Portfolio Segment | Automobile Loan
Average Recorded Investment	39	40	40	39
Interest Income Recognized	1	1	1	1
Consumer Portfolio Segment | Credit Card
Average Recorded Investment	86	100	83	98
Interest Income Recognized	1	1	2	2
Consumer Portfolio Segment | Consumer Other Financing Receivable
Average Recorded Investment		$ 40		$ 56