Loans and Allowance for Loan Losses - Schedule of Activity in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 55,559	$ 50,381	$ 55,461	$ 50,381
Charge-offs	(2,876)	(3,054)	(5,769)	(5,739)
Recoveries	2,606	3,887	4,554	6,192
Provision	1,003	2,446	2,046	2,826
Ending balance	56,292	53,660	56,292	53,660
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	20,406	19,591	21,742	19,246
Charge-offs	(604)	(472)	(764)	(717)
Recoveries	334	249	709	760
Provision	2,412	2,019	861	2,098
Ending balance	22,548	21,387	22,548	21,387
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	25,169	20,796	23,470	21,436
Charge-offs	(389)	(430)	(624)	(433)
Recoveries	1,205	583	1,775	1,067
Provision	(2,674)	1,549	(1,310)	428
Ending balance	23,311	22,498	23,311	22,498
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	2,302	1,763	2,277	1,763
Charge-offs	(140)	(295)	(318)	(657)
Recoveries	9	1,697	81	1,845
Provision	98	(1,298)	229	(1,084)
Ending balance	2,269	1,867	2,269	1,867
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	7,682	8,231	7,972	7,936
Charge-offs	(1,743)	(1,857)	(4,063)	(3,932)
Recoveries	1,058	1,358	1,989	2,520
Provision	1,167	176	2,266	1,384
Ending balance	$ 8,164	$ 7,908	$ 8,164	$ 7,908