Allowance for Credit Losses - Summary of Activity in Allowance for Loan Losses (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 130,200	$ 133,802
Loans charged-off	(40,249)	(36,648)
Charged-off loans recovered	8,771	7,406
Net charge-offs	(31,478)	(29,242)
Provision for loan losses	14,895	25,640
Ending balance	113,617	130,200
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	64,370	73,649
Loans charged-off	(19,837)	(16,103)
Charged-off loans recovered	4,219	4,475
Net charge-offs	(15,618)	(11,628)
Provision for loan losses	2,799	2,349
Ending balance	51,551	64,370
Commercial real estate loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	44,069	34,637
Loans charged-off	(10,846)	(11,688)
Charged-off loans recovered	1,745	272
Net charge-offs	(9,101)	(11,416)
Provision for loan losses	7,375	20,848
Ending balance	42,343	44,069
Residential mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	9,423	9,120
Loans charged-off	(4,446)	(3,518)
Charged-off loans recovered	768	701
Net charge-offs	(3,678)	(2,817)
Provision for loan losses	2,041	3,120
Ending balance	7,786	9,423
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	5,542	8,677
Loans charged-off	(5,120)	(5,339)
Charged-off loans recovered	2,039	1,958
Net charge-offs	(3,081)	(3,381)
Provision for loan losses	1,898	246
Ending balance	4,359	5,542
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	6,796	7,719
Loans charged-off
Charged-off loans recovered
Net charge-offs
Provision for loan losses	782	(923)
Ending balance	$ 7,578	$ 6,796