Loans Receivable, Net - Allowance for Loan Losses and Recorded Investment in Loans by Portfolio Segment and Based on Impairment Method (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Allowance for loan losses:
Balance at beginning of period	$ 16,419	$ 20,934	$ 16,317	$ 20,930
Provision (benefit) charged to operations	300	275	675	805
Charge-offs	(331)	(419)	(689)	(1,158)
Recoveries	146	146	231	359
Balance at end of period	16,534	20,936	16,534	20,936
Ending allowance balance attributed to loans:
Individually evaluated for impairment	2,074		2,074		$ 2,161
Collectively evaluated for impairment	14,460		14,460		14,156
Total ending allowance balance	16,534		16,534		16,317
Loans:
Loans individually evaluated for impairment	43,558		43,558		36,979
Loans collectively evaluated for impairment	1,758,698		1,758,698		1,681,708
Total loans	1,802,256		1,802,256		1,718,687
Residential Real Estate [Member]
Allowance for loan losses:
Balance at beginning of period	4,206	4,290	4,291	4,859
Provision (benefit) charged to operations	(608)	207	(682)	25
Charge-offs	(68)	(205)	(123)	(795)
Recoveries	80	105	124	308
Balance at end of period	3,610	4,397	3,610	4,397
Ending allowance balance attributed to loans:
Individually evaluated for impairment	33		33		88
Collectively evaluated for impairment	3,577		3,577		4,203
Total ending allowance balance	3,610		3,610		4,291
Loans:
Loans individually evaluated for impairment	12,935		12,935		12,879
Loans collectively evaluated for impairment	787,455		787,455		772,562
Total loans	800,390		800,390		785,441
Commercial Real Estate [Member]
Allowance for loan losses:
Balance at beginning of period	9,300	11,413	8,935	10,371
Provision (benefit) charged to operations	(65)	(337)	388	697
Charge-offs	(15)		(103)
Recoveries	9	1	9	9
Balance at end of period	9,229	11,077	9,229	11,077
Ending allowance balance attributed to loans:
Individually evaluated for impairment	1,721		1,721		1,741
Collectively evaluated for impairment	7,508		7,508		7,194
Total ending allowance balance	9,229		9,229		8,935
Loans:
Loans individually evaluated for impairment	27,045		27,045		21,165
Loans collectively evaluated for impairment	671,241		671,241		628,786
Total loans	698,286		698,286		649,951
Consumer [Member]
Allowance for loan losses:
Balance at beginning of period	1,063	1,369	1,146	1,360
Provision (benefit) charged to operations	81	80	175	196
Charge-offs	(248)	(204)	(463)	(313)
Recoveries	56	39	94	41
Balance at end of period	952	1,284	952	1,284
Ending allowance balance attributed to loans:
Individually evaluated for impairment					332
Collectively evaluated for impairment	952		952		814
Total ending allowance balance	952		952		1,146
Loans:
Loans individually evaluated for impairment	2,328		2,328		2,221
Loans collectively evaluated for impairment	190,023		190,023		197,128
Total loans	192,351		192,351		199,349
Commercial and Industrial [Member]
Allowance for loan losses:
Balance at beginning of period	767	1,044	863	1,383
Provision (benefit) charged to operations	918	128	819	(171)
Charge-offs		(10)		(50)
Recoveries	1	1	4	1
Balance at end of period	1,686	1,163	1,686	1,163
Ending allowance balance attributed to loans:
Individually evaluated for impairment	320		320
Collectively evaluated for impairment	1,366		1,366		863
Total ending allowance balance	1,686		1,686		863
Loans:
Loans individually evaluated for impairment	1,250		1,250		714
Loans collectively evaluated for impairment	109,979		109,979		83,232
Total loans	111,229		111,229		83,946
Unallocated [Member]
Allowance for loan losses:
Balance at beginning of period	1,083	2,818	1,082	2,957
Provision (benefit) charged to operations	(26)	197	(25)	58
Balance at end of period	1,057	$ 3,015	1,057	$ 3,015
Ending allowance balance attributed to loans:
Collectively evaluated for impairment	1,057		1,057		1,082
Total ending allowance balance	$ 1,057		$ 1,057		$ 1,082