Loans and Allowance for Credit Losses - Schedule of Activity in Allowance for Loan Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision	$ 1	$ 37
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	20,670	16,565
Charge-offs	44	(1,147)
Recoveries	1,182	792
Provision	2,807	3,296
Ending balance	24,703	19,506
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	17,348	22,401
Charge-offs	710	(168)
Recoveries	167	1,095
Provision	(4,418)	(4,018)
Ending balance	13,807	19,310
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	6,869	4,940
Charge-offs	(1,604)	(1,125)
Recoveries	875	821
Provision	1,309	742
Ending balance	7,449	5,378
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	2,962	3,239
Charge-offs	(374)	21
Recoveries	28	82
Provision	303	17
Ending balance	2,919	3,359
Loans and Leases Receivable Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	47,849	47,145
Charge-offs	(1,224)	(2,419)
Recoveries	2,252	2,790
Provision	1	37
Ending balance	$ 48,878	$ 47,553