Summary of Average Impaired Loans and Leases and Interest Income by Class (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Average Recorded Investment	$ 2,984	$ 3,005	$ 2,997	$ 2,990
Interest Income Recognized	39	69	95	172
Commercial Portfolio Segment | Commercial And Industrial Loans [Member]
Average Recorded Investment	439	540	467	524
Interest Income Recognized	1	15	3	40
Commercial Portfolio Segment | Commercial Mortgage Loans Owner Occupied [Member]
Average Recorded Investment	168	116	157	121
Interest Income Recognized	1	5	3	15
Commercial Portfolio Segment | Commercial Mortgage Loans Non Owner Occupied [Member]
Average Recorded Investment	387	287	356	294
Interest Income Recognized	3	9	7	25
Commercial Portfolio Segment | Commercial Construction
Average Recorded Investment	149	190	176	185
Interest Income Recognized		8	2	19
Commercial Portfolio Segment | Commercial Leases [Member]
Average Recorded Investment	10	18	10	22
Residential Mortgage Loans
Average Recorded Investment	1,276	1,243	1,269	1,219
Interest Income Recognized	13	13	38	34
Consumer Portfolio Segment | Home Equity
Average Recorded Investment	438	446	440	445
Interest Income Recognized	19	17	37	34
Consumer Portfolio Segment | Automobile Loan
Average Recorded Investment	37	42	39	40
Interest Income Recognized	1	1	2	2
Consumer Portfolio Segment | Credit Card
Average Recorded Investment	78	95	81	97
Interest Income Recognized	1	1	3	3
Consumer Portfolio Segment | Consumer Other Financing Receivable
Average Recorded Investment	$ 2	$ 28	$ 2	$ 43