Loans and Other Real Estate - Activity in the Allowance for Loan and Lease Losses by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 38,662	$ 36,604	$ 37,688	$ 35,455
Charge-offs	(809)	(753)	(1,738)	(2,966)
Recoveries	266	396	1,661	982
Provision	536	1,046	1,044	3,822
Ending Balance	38,655	37,293	38,655	37,293
Commercial, secured by real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	28,095	26,174	27,881	25,704
Charge-offs	(314)	(24)	(501)	(256)
Recoveries	72	135	212	440
Provision	672	1,361	933	1,758
Ending Balance	28,525	27,646	28,525	27,646
Commercial, industrial and other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	2,633	2,012	1,742	2,313
Charge-offs	(425)	(151)	(610)	(1,452)
Recoveries	32	177	1,076	273
Provision	218	(70)	250	834
Ending Balance	2,458	1,968	2,458	1,968
Equipment finance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	1,055	1,264	987	630
Charge-offs	0	(368)	(380)	(463)
Recoveries	0	2	2	7
Provision	55	(12)	501	712
Ending Balance	1,110	886	1,110	886
Real estate - residential mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	1,606	1,585	1,566	1,557
Charge-offs	0	(38)	(50)	(131)
Recoveries	55	2	66	7
Provision	(57)	(62)	22	54
Ending Balance	1,604	1,487	1,604	1,487
Real estate - construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	2,708	3,063	3,015	2,731
Charge-offs	0	0	0	(248)
Recoveries	39	4	104	12
Provision	(186)	(166)	(558)	406
Ending Balance	2,561	2,901	2,561	2,901
Home equity and consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	2,565	2,506	2,497	2,520
Charge-offs	(70)	(172)	(197)	(416)
Recoveries	68	76	201	243
Provision	(166)	(5)	(104)	58
Ending Balance	$ 2,397	$ 2,405	$ 2,397	$ 2,405