Loans and Leases and the Allowance for Credit Losses - Additional Information (Detail) (USD $)	6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Residential Mortgage Loans [Member]	Dec. 30, 2012 Residential Mortgage Loans [Member]	Jun. 30, 2013 Commercial Real Estate [Member]	Dec. 30, 2012 Commercial Real Estate [Member]
Loans And Leases Receivable [Line Items]
Contractual principal and interest payments	$ 395,000,000		$ 447,000,000
Purchased impaired loans as a percentage of total assets	Less than 1% of the Company's assets		Less than 1% of the Company's assets
Mortgage loans held for sale				809,000,000	1,200,000,000
Mortgage loan held for sale to Ginnie Mae	1,000,000,000
Commercial mortgage loans held for sale						133,000,000	200,000,000
Consumer loans held for sale	1,500,000,000
Loan delinquent period	90 days or more
Maturity period of line of credit	More than 150 days
Payment defualt for troubled debt restructuring	$ 24,000,000	$ 11,000,000