Loans and Allowance for Loan Losses - Schedule of Activity in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 56,292	$ 53,660	$ 55,461	$ 50,381
Charge-offs	(2,716)	(4,261)	(8,485)	(10,000)
Recoveries	1,897	2,564	6,451	8,756
Provision	1,437	750	3,483	3,576
Ending balance	56,910	52,713	56,910	52,713
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	22,548	21,387	21,742	19,246
Charge-offs	(420)	(1,662)	(1,184)	(2,378)
Recoveries	374	467	1,083	1,227
Provision	(373)	(473)	488	1,624
Ending balance	22,129	19,719	22,129	19,719
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	23,311	22,498	23,470	21,436
Charge-offs	(191)	(241)	(815)	(675)
Recoveries	669	944	2,444	2,011
Provision	465	(309)	(845)	120
Ending balance	24,254	22,892	24,254	22,892
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	2,269	1,867	2,277	1,763
Charge-offs	(384)	(284)	(702)	(941)
Recoveries	26	45	107	1,890
Provision	452	292	681	(792)
Ending balance	2,363	1,920	2,363	1,920
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	8,164	7,908	7,972	7,936
Charge-offs	(1,721)	(2,074)	(5,784)	(6,006)
Recoveries	828	1,108	2,817	3,628
Provision	893	1,240	3,159	2,624
Ending balance	$ 8,164	$ 8,182	$ 8,164	$ 8,182