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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Allowance for loan losses:
Balance at beginning of period	$ 16,151	$ 16,214	$ 15,183	$ 16,722
Provision (benefit) charged to operations	1,165	662	1,865	1,225
Charge-offs	(1,299)	(223)	(1,504)	(1,395)
Recoveries	540	25	1,013	126
Balance at end of period	16,557	16,678	16,557	16,678
Ending allowance balance attributed to loans:
Individually evaluated for impairment	616		616		$ 510
Collectively evaluated for impairment	15,941		15,941		14,673
Total ending allowance balance	16,557		16,557		15,183
Loans:
Loans individually evaluated for impairment	41,290		41,290		31,042
Loans collectively evaluated for impairment	3,857,327		3,857,327		3,790,844
Total loans	3,898,617		3,898,617		3,821,886
Residential Real Estate
Allowance for loan losses:
Balance at beginning of period	1,569	6,555	2,245	6,590
Provision (benefit) charged to operations	639	(480)	12	(491)
Charge-offs	(1,152)	(74)	(1,201)	(152)
Recoveries	436	5	436	59
Balance at end of period	1,492	6,006	1,492	6,006
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0		0		266
Collectively evaluated for impairment	1,492		1,492		1,979
Total ending allowance balance	1,492		1,492		2,245
Loans:
Loans individually evaluated for impairment	13,098		13,098		13,306
Loans collectively evaluated for impairment	1,731,103		1,731,103		1,699,167
Total loans	1,744,201		1,744,201		1,712,473
Commercial Real Estate - Owner Occupied
Allowance for loan losses:
Balance at beginning of period	3,449	2,363	2,999	2,292
Provision (benefit) charged to operations	(342)	390	48	1,429
Charge-offs	(23)	(42)	(73)	(1,010)
Recoveries	13		123
Balance at end of period	3,097	2,711	3,097	2,711
Ending allowance balance attributed to loans:
Individually evaluated for impairment					0
Collectively evaluated for impairment	3,097		3,097		2,999
Total ending allowance balance	3,097		3,097		2,999
Loans:
Loans individually evaluated for impairment	10,896		10,896		11,123
Loans collectively evaluated for impairment	545,284		545,284		523,091
Total loans	556,180		556,180		534,214
Commercial Real Estate - Investor
Allowance for loan losses:
Balance at beginning of period	7,361	4,302	6,361	4,873
Provision (benefit) charged to operations	1,090	410	2,083	(170)
Charge-offs	(84)	0	(84)	0
Recoveries	0	1	7	10
Balance at end of period	8,367	4,713	8,367	4,713
Ending allowance balance attributed to loans:
Individually evaluated for impairment	616		616		119
Collectively evaluated for impairment	7,751		7,751		6,242
Total ending allowance balance	8,367		8,367		6,361
Loans:
Loans individually evaluated for impairment	13,861		13,861		3,789
Loans collectively evaluated for impairment	1,107,081		1,107,081		1,128,286
Total loans	1,120,942		1,120,942		1,132,075
Consumer
Allowance for loan losses:
Balance at beginning of period	1,136	1,081	1,110	1,095
Provision (benefit) charged to operations	(244)	70	(224)	30
Charge-offs	(40)	(63)	(58)	(66)
Recoveries	78	19	102	48
Balance at end of period	930	1,107	930	1,107
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0		0		125
Collectively evaluated for impairment	930		930		985
Total ending allowance balance	930		930		1,110
Loans:
Loans individually evaluated for impairment	2,512		2,512		2,556
Loans collectively evaluated for impairment	281,157		281,157		287,999
Total loans	283,669		283,669		290,555
Commercial and Industrial
Allowance for loan losses:
Balance at beginning of period	2,080	1,380	2,037	1,639
Provision (benefit) charged to operations	160	(127)	(41)	(272)
Charge-offs	0	(44)	(88)	(167)
Recoveries	13	0	345	9
Balance at end of period	2,253	1,209	2,253	1,209
Ending allowance balance attributed to loans:
Individually evaluated for impairment					0
Collectively evaluated for impairment	2,253		2,253		2,037
Total ending allowance balance	2,253		2,253		2,037
Loans:
Loans individually evaluated for impairment	923		923		268
Loans collectively evaluated for impairment	192,702		192,702		152,301
Total loans	193,625		193,625		152,569
Unallocated
Allowance for loan losses:
Balance at beginning of period	556	533	431	233
Provision (benefit) charged to operations	(138)	399	(13)	699
Balance at end of period	418	$ 932	418	$ 932
Ending allowance balance attributed to loans:
Collectively evaluated for impairment	418		418		431
Total ending allowance balance	418		418		431
Loans:
Total loans	$ 0		$ 0		$ 0