Loans Receivable, Net - Allowance for Loan Losses and Recorded Investment in Loans by Portfolio Segment and Based on Impairment Method (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for loan losses:
Balance at beginning of year	$ 20,930	$ 20,510	$ 18,230
Provision (benefit) charged to operations	2,630	2,800	7,900
Charge-offs	(7,827)	(3,521)	(7,084)
Recoveries	584	1,141	1,464
Balance at end of year	16,317	20,930	20,510
Ending allowance balance attributed to loans:
Individually evaluated for impairment	2,161	3,647
Collectively evaluated for impairment	14,156	17,283
Total ending allowance balance	16,317	20,930
Loans:
Loans individually evaluated for impairment	36,979	39,903
Loans collectively evaluated for impairment	1,681,708	1,531,676
Total loans	1,718,687	1,571,579
Residential Real Estate [Member]
Allowance for loan losses:
Balance at beginning of year	4,859	5,241
Provision (benefit) charged to operations	5,862	1,236
Charge-offs	(6,955)	(2,444)
Recoveries	525	826
Balance at end of year	4,291	4,859
Ending allowance balance attributed to loans:
Individually evaluated for impairment	88	2
Collectively evaluated for impairment	4,203	4,857
Total ending allowance balance	4,291	4,859
Loans:
Loans individually evaluated for impairment	12,879	18,192
Loans collectively evaluated for impairment	772,562	763,214
Total loans	785,441	781,406
Commercial Real Estate [Member]
Allowance for loan losses:
Balance at beginning of year	10,371	8,937
Provision (benefit) charged to operations	(1,122)	1,383
Charge-offs	(323)
Recoveries	9	51
Balance at end of year	8,935	10,371
Ending allowance balance attributed to loans:
Individually evaluated for impairment	1,741	3,612
Collectively evaluated for impairment	7,194	6,759
Total ending allowance balance	8,935	10,371
Loans:
Loans individually evaluated for impairment	21,165	17,643
Loans collectively evaluated for impairment	628,786	511,302
Total loans	649,951	528,945
Consumer [Member]
Allowance for loan losses:
Balance at beginning of year	1,360	2,264
Provision (benefit) charged to operations	211	(297)
Charge-offs	(471)	(842)
Recoveries	46	235
Balance at end of year	1,146	1,360
Ending allowance balance attributed to loans:
Individually evaluated for impairment	332	33
Collectively evaluated for impairment	814	1,327
Total ending allowance balance	1,146	1,360
Loans:
Loans individually evaluated for impairment	2,221	2,961
Loans collectively evaluated for impairment	197,128	197,722
Total loans	199,349	200,683
Commercial and Industrial [Member]
Allowance for loan losses:
Balance at beginning of year	1,383	1,348
Provision (benefit) charged to operations	(446)	241
Charge-offs	(78)	(235)
Recoveries	4	29
Balance at end of year	863	1,383
Ending allowance balance attributed to loans:
Collectively evaluated for impairment	863	1,383
Total ending allowance balance	863	1,383
Loans:
Loans individually evaluated for impairment	714	1,107
Loans collectively evaluated for impairment	83,232	59,438
Total loans	83,946	60,545
Unallocated [Member]
Allowance for loan losses:
Balance at beginning of year	2,957	2,720
Provision (benefit) charged to operations	(1,875)	237
Balance at end of year	1,082	2,957
Ending allowance balance attributed to loans:
Collectively evaluated for impairment	1,082	2,957
Total ending allowance balance	$ 1,082	$ 2,957