Loans and Allowance for Credit Losses - Schedule of Activity in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 50,700	$ 48,878	$ 52,233	$ 47,849
Charge-offs	(2,677)	(3,902)	(6,619)	(6,016)
Recoveries	2,462	2,944	4,780	6,086
Provision	1,319	2,271	1,410	2,272
Ending balance	51,804	50,191	51,804	50,191
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	25,121	24,703	26,347	20,670
Charge-offs	(432)	(1,872)	(1,959)	(2,421)
Recoveries	876	789	1,694	2,564
Provision	(1,409)	(186)	(1,926)	2,621
Ending balance	24,156	23,434	24,156	23,434
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	15,771	13,807	15,993	17,348
Charge-offs	(783)	(514)	(1,062)	(101)
Recoveries	547	1,009	1,387	1,473
Provision	2,673	2,023	1,890	(2,395)
Ending balance	18,208	16,325	18,208	16,325
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,749	2,919	2,051	2,962
Charge-offs	(80)	(22)	(220)	(396)
Recoveries	187	59	213	87
Provision	(397)	(375)	(585)	(72)
Ending balance	1,459	2,581	1,459	2,581
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	8,059	7,449	7,842	6,869
Charge-offs	(1,382)	(1,494)	(3,378)	(3,098)
Recoveries	852	1,087	1,486	1,962
Provision	452	809	2,031	2,118
Ending balance	$ 7,981	$ 7,851	$ 7,981	$ 7,851