Summary of Average Impaired Loans and Leases and Interest Income by Class (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Average Recorded Investment	$ 2,969	$ 2,968	$ 3,200
Interest Income Recognized	96	83	74
Commercial Portfolio Segment | Commercial And Industrial Loans [Member]
Average Recorded Investment	448	532
Interest Income Recognized	4	5
Commercial Portfolio Segment | Commercial Mortgage Loans Owner Occupied [Member]
Average Recorded Investment	156	117
Interest Income Recognized	4	2
Commercial Portfolio Segment | Commercial Mortgage Loans Non Owner Occupied [Member]
Average Recorded Investment	361	288
Interest Income Recognized	10	5
Commercial Portfolio Segment | Commercial Construction
Average Recorded Investment	160	198
Interest Income Recognized	2	3
Commercial Portfolio Segment | Commercial Leases [Member]
Average Recorded Investment	10	16
Residential Mortgage Loans
Average Recorded Investment	1,276	1,217
Interest Income Recognized	47	41
Consumer Portfolio Segment | Home Equity
Average Recorded Investment	439	444
Interest Income Recognized	24	23
Consumer Portfolio Segment | Automobile Loan
Average Recorded Investment	38	41
Interest Income Recognized	1	1
Consumer Portfolio Segment | Credit Card
Average Recorded Investment	80	94
Interest Income Recognized	4	3
Consumer Portfolio Segment | Consumer Other Financing Receivable
Average Recorded Investment	$ 1	$ 21