Loans and the Allowance for Credit Losses - Summary of Changes in Allowance for Credit 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]
Allowance for loan losses, beginning balance			$ 48,948	$ 45,284
Allowance for loan commitments, beginning balance			741	574
Total beginning allowance for credit losses			49,689	45,858
Provision for loan losses			4,229	3,843
Provision for loan commitments			1,025	33
Total provision for credit losses	$ 2,747	$ 1,708	5,254	3,876
Charge-offs			(4,866)	(4,959)
Recoveries			2,548	3,470
Net charge-offs			(2,318)	(1,489)
Allowance for loan losses, ending balance	50,859	47,638	50,859	47,638
Allowance for loan commitments, ending balance	1,766	607	1,766	607
Total ending allowance for credit losses	52,625	48,245	52,625	48,245
Commercial Real Estate - Land and Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			4,039	3,117
Allowance for loan commitments, beginning balance			169	119
Total beginning allowance for credit losses			4,208	3,236
Provision for loan losses			(538)	1,465
Provision for loan commitments			18	44
Total provision for credit losses			(520)	1,509
Charge-offs				(136)
Recoveries			200	264
Net charge-offs			200	128
Allowance for loan losses, ending balance	3,701	4,710	3,701	4,710
Allowance for loan commitments, ending balance	187	163	187	163
Total ending allowance for credit losses	3,888	4,873	3,888	4,873
Commercial Real Estate - Improved Property [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			20,848	21,166
Allowance for loan commitments, beginning balance			33	26
Total beginning allowance for credit losses			20,881	21,192
Provision for loan losses			1,459	(1,774)
Provision for loan commitments			(9)	(8)
Total provision for credit losses			1,450	(1,782)
Charge-offs			(285)	(692)
Recoveries			345	776
Net charge-offs			60	84
Allowance for loan losses, ending balance	22,367	19,476	22,367	19,476
Allowance for loan commitments, ending balance	24	18	24	18
Total ending allowance for credit losses	22,391	19,494	22,391	19,494
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			12,114	9,414
Allowance for loan commitments, beginning balance			262	173
Total beginning allowance for credit losses			12,376	9,587
Provision for loan losses			1,309	2,100
Provision for loan commitments			995	2
Total provision for credit losses			2,304	2,102
Charge-offs			(1,025)	(616)
Recoveries			489	636
Net charge-offs			(536)	20
Allowance for loan losses, ending balance	12,887	11,534	12,887	11,534
Allowance for loan commitments, ending balance	1,257	175	1,257	175
Total ending allowance for credit losses	14,144	11,709	14,144	11,709
Deposit Overdraft [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			972	821
Total beginning allowance for credit losses			972	821
Provision for loan losses			1,119	439
Total provision for credit losses			1,119	439
Charge-offs			(860)	(541)
Recoveries			215	197
Net charge-offs			(645)	(344)
Allowance for loan losses, ending balance	1,446	916	1,446	916
Total ending allowance for credit losses	1,446	916	1,446	916
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			3,822	3,206
Allowance for loan commitments, beginning balance			12	7
Total beginning allowance for credit losses			3,834	3,213
Provision for loan losses			124	944
Provision for loan commitments			1	2
Total provision for credit losses			125	946
Charge-offs			(679)	(509)
Recoveries			188	252
Net charge-offs			(491)	(257)
Allowance for loan losses, ending balance	3,455	3,893	3,455	3,893
Allowance for loan commitments, ending balance	13	9	13	9
Total ending allowance for credit losses	3,468	3,902	3,468	3,902
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			2,797	3,063
Allowance for loan commitments, beginning balance			39	37
Total beginning allowance for credit losses			2,836	3,100
Provision for loan losses			333	615
Provision for loan commitments			(3)
Total provision for credit losses			330	615
Charge-offs			(1,344)	(1,793)
Recoveries			896	1,066
Net charge-offs			(448)	(727)
Allowance for loan losses, ending balance	2,682	2,951	2,682	2,951
Allowance for loan commitments, ending balance	36	37	36	37
Total ending allowance for credit losses	2,718	2,988	2,718	2,988
Home Equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			4,356	4,497
Allowance for loan commitments, beginning balance			226	212
Total beginning allowance for credit losses			4,582	4,709
Provision for loan losses			423	54
Provision for loan commitments			23	(7)
Total provision for credit losses			446	47
Charge-offs			(673)	(672)
Recoveries			215	279
Net charge-offs			(458)	(393)
Allowance for loan losses, ending balance	4,321	4,158	4,321	4,158
Allowance for loan commitments, ending balance	249	205	249	205
Total ending allowance for credit losses	$ 4,570	$ 4,363	$ 4,570	$ 4,363