Loans and Other Real Estate - Allowance for Loan and Lease Losses by Portfolio Segment (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 5,769,127		$ 5,140,940
Ending Balance: Individually evaluated for impairment	271		352
Ending Balance	57,839	$ 48,884	40,003	$ 38,662	$ 37,979	$ 37,688
Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	32,355		22,124
Ending Balance: Collectively evaluated for impairment	5,728,764		5,110,068
Ending Balance: Loans acquired with deteriorated credit quality	8,008		8,748
Total loans	5,769,127		5,140,940
Ending Balance: Individually evaluated for impairment	271		352
Ending Balance: Collectively evaluated for impairment	57,568		39,651
Ending Balance	57,839		40,003
Commercial, secured by real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	3,961,476		3,589,593
Ending Balance: Individually evaluated for impairment	187		228
Ending Balance	43,280	34,793	28,950	28,095	27,515	27,881
Commercial, secured by real estate | Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	27,467		15,948
Ending Balance: Collectively evaluated for impairment	3,928,582		3,567,540
Ending Balance: Loans acquired with deteriorated credit quality	5,427		6,105
Total loans	3,961,476		3,589,593
Ending Balance: Individually evaluated for impairment	187		228
Ending Balance: Collectively evaluated for impairment	43,093		28,722
Ending Balance	43,280		28,950
Commercial, industrial and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	402,239		431,934
Ending Balance: Individually evaluated for impairment	5		5
Ending Balance	4,698	5,489	3,289	2,633	2,592	1,742
Commercial, industrial and other | Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment			1,504
Ending Balance: Collectively evaluated for impairment			429,486
Ending Balance: Loans acquired with deteriorated credit quality			944
Total loans			431,934
Ending Balance: Individually evaluated for impairment	5		5
Ending Balance: Collectively evaluated for impairment	4,693		3,284
Ending Balance	4,698		3,289
Commercial, Industrial and Other (including PPP)
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	728,238
Commercial, Industrial and Other (including PPP) | Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	1,410
Ending Balance: Collectively evaluated for impairment	725,952
Ending Balance: Loans acquired with deteriorated credit quality	876
Total loans	728,238
Equipment finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	115,651		111,076
Ending Balance: Individually evaluated for impairment	7		10
Ending Balance	2,971	1,257	957	1,055	947	987
Equipment finance | Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	17		23
Ending Balance: Collectively evaluated for impairment	115,634		111,053
Ending Balance: Loans acquired with deteriorated credit quality	0		0
Total loans	115,651		111,076
Ending Balance: Individually evaluated for impairment	7		10
Ending Balance: Collectively evaluated for impairment	2,964		947
Ending Balance	2,971		957
Real estate - residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	334,455		335,191
Ending Balance: Individually evaluated for impairment	67		104
Ending Balance	1,436	1,600	1,725	1,606	1,564	1,566
Real estate - residential mortgage | Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	2,160		2,315
Ending Balance: Collectively evaluated for impairment	331,883		332,486
Ending Balance: Loans acquired with deteriorated credit quality	412		390
Total loans	334,455		335,191
Ending Balance: Individually evaluated for impairment	67		104
Ending Balance: Collectively evaluated for impairment	1,369		1,621
Ending Balance	1,436		1,725
Real estate - construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	299,441		335,169
Ending Balance: Individually evaluated for impairment	0		0
Ending Balance	3,119	3,344	2,672	2,708	2,887	3,015
Real estate - construction | Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	694		1,663
Ending Balance: Collectively evaluated for impairment	297,967		332,722
Ending Balance: Loans acquired with deteriorated credit quality	780		784
Total loans	299,441		335,169
Ending Balance: Individually evaluated for impairment	0		0
Ending Balance: Collectively evaluated for impairment	3,119		2,672
Ending Balance	3,119		2,672
Home equity and consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	329,866		337,977
Ending Balance: Individually evaluated for impairment	5		5
Ending Balance	2,335	$ 2,401	2,410	$ 2,565	$ 2,474	$ 2,497
Home equity and consumer | Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	607		671
Ending Balance: Collectively evaluated for impairment	328,746		336,781
Ending Balance: Loans acquired with deteriorated credit quality	513		525
Total loans	329,866		337,977
Ending Balance: Individually evaluated for impairment	5		5
Ending Balance: Collectively evaluated for impairment	2,330		2,405
Ending Balance	$ 2,335		$ 2,410