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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Allowance for loan losses:
Balance at beginning of period	$ 16,557	$ 16,678	$ 15,183	$ 16,722
Provision (benefit) charged to operations	1,165	888	3,030	2,113
Charge-offs	(1,357)	(2,116)	(2,861)	(3,511)
Recoveries	219	167	1,232	293
Balance at end of period	16,584	15,617	16,584	15,617
Ending allowance balance attributed to loans:
Individually evaluated for impairment	616		616		$ 510
Collectively evaluated for impairment	15,968		15,968		14,673
Total ending allowance balance	16,584		16,584		15,183
Loans:
Loans individually evaluated for impairment	44,927		44,927		31,042
Loans collectively evaluated for impairment	3,854,800		3,854,800		3,790,844
Total loans	3,899,727		3,899,727		3,821,886
Residential Real Estate
Allowance for loan losses:
Balance at beginning of period	1,492	6,006	2,245	6,590
Provision (benefit) charged to operations	1,465	(376)	1,477	(867)
Charge-offs	(1,284)	(167)	(2,485)	(319)
Recoveries	128	6	564	65
Balance at end of period	1,801	5,469	1,801	5,469
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0		0		266
Collectively evaluated for impairment	1,801		1,801		1,979
Total ending allowance balance	1,801		1,801		2,245
Loans:
Loans individually evaluated for impairment	12,484		12,484		13,306
Loans collectively evaluated for impairment	1,737,471		1,737,471		1,699,167
Total loans	1,749,955		1,749,955		1,712,473
Commercial Real Estate - Owner Occupied
Allowance for loan losses:
Balance at beginning of period	3,097	2,711	2,999	2,292
Provision (benefit) charged to operations	119	(168)	167	1,261
Charge-offs	0	0	(73)	(1,010)
Recoveries	0		123
Balance at end of period	3,216	2,543	3,216	2,543
Ending allowance balance attributed to loans:
Individually evaluated for impairment					0
Collectively evaluated for impairment	3,216		3,216		2,999
Total ending allowance balance	3,216		3,216		2,999
Loans:
Loans individually evaluated for impairment	11,537		11,537		11,123
Loans collectively evaluated for impairment	542,434		542,434		523,091
Total loans	553,971		553,971		534,214
Commercial Real Estate - Investor
Allowance for loan losses:
Balance at beginning of period	8,367	4,713	6,361	4,873
Provision (benefit) charged to operations	81	104	2,164	(56)
Charge-offs	0	0	(84)	0
Recoveries	24	0	31	0
Balance at end of period	8,472	4,817	8,472	4,817
Ending allowance balance attributed to loans:
Individually evaluated for impairment	616		616		119
Collectively evaluated for impairment	7,856		7,856		6,242
Total ending allowance balance	8,472		8,472		6,361
Loans:
Loans individually evaluated for impairment	17,535		17,535		3,789
Loans collectively evaluated for impairment	1,115,583		1,115,583		1,128,286
Total loans	1,133,118		1,133,118		1,132,075
Consumer
Allowance for loan losses:
Balance at beginning of period	930	1,107	1,110	1,095
Provision (benefit) charged to operations	(122)	(130)	(346)	(98)
Charge-offs	(67)	(80)	(125)	(146)
Recoveries	17	0	119	46
Balance at end of period	758	897	758	897
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0		0		125
Collectively evaluated for impairment	758		758		985
Total ending allowance balance	758		758		1,110
Loans:
Loans individually evaluated for impairment	2,478		2,478		2,556
Loans collectively evaluated for impairment	276,785		276,785		287,999
Total loans	279,263		279,263		290,555
Commercial and Industrial
Allowance for loan losses:
Balance at beginning of period	2,253	1,209	2,037	1,639
Provision (benefit) charged to operations	(180)	1,949	(221)	1,665
Charge-offs	(6)	(1,869)	(94)	(2,036)
Recoveries	50	161	395	182
Balance at end of period	2,117	1,450	2,117	1,450
Ending allowance balance attributed to loans:
Individually evaluated for impairment					0
Collectively evaluated for impairment	2,117		2,117		2,037
Total ending allowance balance	2,117		2,117		2,037
Loans:
Loans individually evaluated for impairment	893		893		268
Loans collectively evaluated for impairment	182,527		182,527		152,301
Total loans	183,420		183,420		152,569
Unallocated
Allowance for loan losses:
Balance at beginning of period	418	932	431	233
Provision (benefit) charged to operations	(198)	(491)	(211)	208
Balance at end of period	220	$ 441	220	$ 441
Ending allowance balance attributed to loans:
Collectively evaluated for impairment	220		220		431
Total ending allowance balance	220		220		431
Loans:
Total loans	$ 0		$ 0		$ 0