Summary of Average Impaired Loans and Leases and Interest Income by Class (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Average Recorded Investment	$ 2,993	$ 2,959
Interest Income Recognized	24	48
Commercial Portfolio Segment | Commercial And Industrial Loans [Member]
Average Recorded Investment	494	509
Interest Income Recognized	1	13
Commercial Portfolio Segment | Commercial Mortgage Loans Owner Occupied [Member]
Average Recorded Investment	139	109
Interest Income Recognized	1	5
Commercial Portfolio Segment | Commercial Mortgage Loans Non Owner Occupied [Member]
Average Recorded Investment	320	277
Interest Income Recognized	2	8
Commercial Portfolio Segment | Commercial Construction
Average Recorded Investment	202	206
Interest Income Recognized	1	5
Commercial Portfolio Segment | Commercial Leases [Member]
Average Recorded Investment	11	14
Residential Mortgage Loans
Average Recorded Investment	1,262	1,196
Interest Income Recognized	12	10
Consumer Portfolio Segment | Home Equity
Average Recorded Investment	444	441
Interest Income Recognized	6	6
Consumer Portfolio Segment | Automobile Loan
Average Recorded Investment	41	39
Consumer Portfolio Segment | Credit Card
Average Recorded Investment	80	86
Interest Income Recognized	1	1
Consumer Portfolio Segment | Consumer Other Financing Receivable
Average Recorded Investment		$ 82