Loans and Allowance for Loan Losses - Schedule of Activity in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 49,808	$ 52,233
Charge-offs	(3,239)	(3,942)
Recoveries	2,918	2,318
Provision	347	91
Ending balance	49,834	50,700
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	21,481	26,347
Charge-offs	(470)	(1,527)
Recoveries	603	818
Provision	494	(517)
Ending balance	22,108	25,121
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	18,173	15,993
Charge-offs	(568)	(279)
Recoveries	1,225	840
Provision	(877)	(783)
Ending balance	17,953	15,771
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,643	2,051
Charge-offs	(414)	(140)
Recoveries	79	26
Provision	428	(188)
Ending balance	1,736	1,749
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	8,511	7,842
Charge-offs	(1,787)	(1,996)
Recoveries	1,011	634
Provision	302	1,579
Ending balance	$ 8,037	$ 8,059