Loans Receivable, Net - Allowance for Loan Losses and Recorded Investment in Loans by Portfolio Segment and Based on Impairment Method Excluding PCI Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Allowance for loan losses:
Balance at beginning of period	$ 16,705	$ 16,817	$ 16,577	$ 15,721
Provision (benefit) charged to operations	356	706	976	2,077
Charge-offs	(1,138)	(1,284)	(2,006)	(1,817)
Recoveries	212	452	588	710
Balance at end of period	16,135	16,691	16,135	16,691
Ending allowance balance attributed to loans:
Individually evaluated for impairment	565		565		$ 0
Collectively evaluated for impairment	15,570		15,570		16,577
Total ending allowance balance	16,135		16,135		16,577
Loans:
Loans individually evaluated for impairment	28,567		28,567		29,797
Loans collectively evaluated for impairment	5,909,886		5,909,886		5,550,015
Total loans	5,938,453		5,938,453		5,579,812
Commercial and Industrial
Allowance for loan losses:
Balance at beginning of period	1,647	2,251	1,609	1,801
Provision (benefit) charged to operations	(34)	(186)	(53)	283
Charge-offs	0	(13)	0	(56)
Recoveries	26	28	83	52
Balance at end of period	1,639	2,080	1,639	2,080
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0		0		0
Collectively evaluated for impairment	1,639		1,639		1,609
Total ending allowance balance	1,639		1,639		1,609
Loans:
Loans individually evaluated for impairment	248		248		1,626
Loans collectively evaluated for impairment	391,340		391,340		303,368
Total loans	391,588		391,588		304,994
Commercial Real Estate – Owner Occupied
Allowance for loan losses:
Balance at beginning of period	3,438	2,871	2,277	3,175
Provision (benefit) charged to operations	(439)	(616)	1,112	(923)
Charge-offs	(132)	(90)	(522)	(90)
Recoveries	1	175	1	178
Balance at end of period	2,868	2,340	2,868	2,340
Ending allowance balance attributed to loans:
Individually evaluated for impairment	565		565		0
Collectively evaluated for impairment	2,303		2,303		2,277
Total ending allowance balance	2,868		2,868		2,277
Loans:
Loans individually evaluated for impairment	6,598		6,598		5,395
Loans collectively evaluated for impairment	764,132		764,132		734,980
Total loans	770,730		770,730		740,375
Commercial Real Estate – Investor
Allowance for loan losses:
Balance at beginning of period	8,242	8,838	8,770	7,952
Provision (benefit) charged to operations	117	1,166	(685)	2,045
Charge-offs	(65)	(978)	(86)	(1,101)
Recoveries	112	32	407	162
Balance at end of period	8,406	9,058	8,406	9,058
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0		0		0
Collectively evaluated for impairment	8,406		8,406		8,770
Total ending allowance balance	8,406		8,406		8,770
Loans:
Loans individually evaluated for impairment	8,169		8,169		9,738
Loans collectively evaluated for impairment	2,123,593		2,123,593		2,005,472
Total loans	2,131,762		2,131,762		2,015,210
Residential Real Estate
Allowance for loan losses:
Balance at beginning of period	1,965	2,138	2,413	1,804
Provision (benefit) charged to operations	729	8	705	501
Charge-offs	(768)	(157)	(1,193)	(401)
Recoveries	40	137	41	222
Balance at end of period	1,966	2,126	1,966	2,126
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0		0		0
Collectively evaluated for impairment	1,966		1,966		2,413
Total ending allowance balance	1,966		1,966		2,413
Loans:
Loans individually evaluated for impairment	10,179		10,179		10,064
Loans collectively evaluated for impairment	2,183,310		2,183,310		2,034,222
Total loans	2,193,489		2,193,489		2,044,286
Consumer
Allowance for loan losses:
Balance at beginning of period	367	507	486	614
Provision (benefit) charged to operations	285	(15)	175	(15)
Charge-offs	(173)	(46)	(205)	(169)
Recoveries	33	80	56	96
Balance at end of period	512	526	512	526
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0		0		0
Collectively evaluated for impairment	512		512		486
Total ending allowance balance	512		512		486
Loans:
Loans individually evaluated for impairment	3,373		3,373		2,974
Loans collectively evaluated for impairment	447,511		447,511		471,973
Total loans	450,884		450,884		474,947
Unallocated
Allowance for loan losses:
Balance at beginning of period	1,046	212	1,022	375
Provision (benefit) charged to operations	(302)	349	(278)	186
Charge-offs	0	0
Recoveries	0	0
Balance at end of period	744	$ 561	744	$ 561
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0		0		0
Collectively evaluated for impairment	744		744		1,022
Total ending allowance balance	744		744		1,022
Loans:
Loans individually evaluated for impairment	0		0		0
Loans collectively evaluated for impairment	0		0		0
Total loans	$ 0		$ 0		$ 0