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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Allowance for loan losses:
Balance at beginning of period	$ 16,534	$ 20,936	$ 16,317	$ 20,930
Provision (benefit) charged to operations	300	1,000	975	1,805
Charge-offs	(211)	(5,783)	(900)	(6,915)
Recoveries	15	157	246	490
Balance at end of period	16,638	16,310	16,638	16,310
Ending allowance balance attributed to loans:
Individually evaluated for impairment	2,400		2,400		$ 2,161
Collectively evaluated for impairment	14,238		14,238		14,156
Total ending allowance balance	16,638		16,638		16,317
Loans:
Loans individually evaluated for impairment	45,573		45,573		36,979
Loans collectively evaluated for impairment	1,919,947		1,919,947		1,681,708
Total loans	1,965,520		1,965,520		1,718,687
Residential Real Estate [Member]
Allowance for loan losses:
Balance at beginning of period	3,610	4,397	4,291	4,859
Provision (benefit) charged to operations	1,602	4,982	920	5,007
Charge-offs	(51)	(5,424)	(174)	(6,193)
Recoveries		152	124	434
Balance at end of period	5,161	4,107	5,161	4,107
Ending allowance balance attributed to loans:
Individually evaluated for impairment	67		67		88
Collectively evaluated for impairment	5,094		5,094		4,203
Total ending allowance balance	5,161		5,161		4,291
Loans:
Loans individually evaluated for impairment	12,377		12,377		12,879
Loans collectively evaluated for impairment	826,118		826,118		772,562
Total loans	838,495		838,495		785,441
Commercial Real Estate [Member]
Allowance for loan losses:
Balance at beginning of period	9,229	11,077	8,935	10,371
Provision (benefit) charged to operations	(892)	(2,510)	(504)	(1,813)
Charge-offs		(323)	(103)	(323)
Recoveries	10		19	9
Balance at end of period	8,347	8,244	8,347	8,244
Ending allowance balance attributed to loans:
Individually evaluated for impairment	1,991		1,991		1,741
Collectively evaluated for impairment	6,356		6,356		7,194
Total ending allowance balance	8,347		8,347		8,935
Loans:
Loans individually evaluated for impairment	29,573		29,573		21,165
Loans collectively evaluated for impairment	773,767		773,767		628,786
Total loans	803,340		803,340		649,951
Consumer [Member]
Allowance for loan losses:
Balance at beginning of period	952	1,284	1,146	1,360
Provision (benefit) charged to operations	73	173	249	368
Charge-offs	(101)	(35)	(564)	(348)
Recoveries	3	4	96	46
Balance at end of period	927	1,426	927	1,426
Ending allowance balance attributed to loans:
Individually evaluated for impairment	22		22		332
Collectively evaluated for impairment	905		905		814
Total ending allowance balance	927		927		1,146
Loans:
Loans individually evaluated for impairment	2,373		2,373		2,221
Loans collectively evaluated for impairment	191,933		191,933		197,128
Total loans	194,306		194,306		199,349
Commercial and Industrial [Member]
Allowance for loan losses:
Balance at beginning of period	1,686	1,163	863	1,383
Provision (benefit) charged to operations	(101)	(123)	717	(293)
Charge-offs	(59)	(1)	(59)	(51)
Recoveries	2	1	7	1
Balance at end of period	1,528	1,040	1,528	1,040
Ending allowance balance attributed to loans:
Individually evaluated for impairment	320		320
Collectively evaluated for impairment	1,208		1,208		863
Total ending allowance balance	1,528		1,528		863
Loans:
Loans individually evaluated for impairment	1,250		1,250		714
Loans collectively evaluated for impairment	128,129		128,129		83,232
Total loans	129,379		129,379		83,946
Unallocated [Member]
Allowance for loan losses:
Balance at beginning of period	1,057	3,015	1,082	2,957
Provision (benefit) charged to operations	(382)	(1,522)	(407)	(1,464)
Balance at end of period	675	$ 1,493	675	$ 1,493
Ending allowance balance attributed to loans:
Collectively evaluated for impairment	675		675		1,082
Total ending allowance balance	$ 675		$ 675		$ 1,082