Loans, Leases and Allowance for Credit Losses - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 TDR loans [Member]	Dec. 31, 2013 TDR loans [Member]
Leases [Line Items]
Reduction in interest income due to nonaccrual loans	$ 0.3	$ 1.2	$ 1.3	$ 2.5
Minimum Period Of Internal Loss Allowance Calculation Model			1 year
Maximum Period Of Internal Loss Allowance Calculation Model			5 years
Loan commitments outstanding					0	0
Loan purchases	$ 16.7	$ 87.5	$ 32.3	$ 130.5