Loans and Other Real Estate - Activity in the Allowance for Loan and Lease Losses by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 37,688	$ 35,455
Charge-offs	516	1,250
Recoveries	299	155
Provision	508	1,284
Ending Balance	37,979	35,644
Commercial, secured by real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	27,881	25,704
Charge-offs	(187)	(22)
Recoveries	115	31
Provision	(294)	104
Ending Balance	27,515	25,817
Commercial, industrial and other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	1,742	2,313
Charge-offs	(147)	(1,012)
Recoveries	97	20
Provision	900	447
Ending Balance	2,592	1,768
Equipment finance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	987	630
Charge-offs	(87)	(23)
Recoveries	2	2
Provision	45	433
Ending Balance	947	1,042
Real estate - residential mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	1,566	1,557
Charge-offs	(50)	(93)
Recoveries	9	2
Provision	39	123
Ending Balance	1,564	1,589
Real estate - construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	3,015	2,731
Charge-offs	0	0
Recoveries	5	5
Provision	(133)	196
Ending Balance	2,887	2,932
Home equity and consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	2,497	2,520
Charge-offs	(45)	(100)
Recoveries	71	95
Provision	(49)	(19)
Ending Balance	$ 2,474	$ 2,496