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	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Allowance for loan losses:
Balance at beginning of period	$ 20,934	$ 20,494	$ 20,930	$ 20,510
Provision (benefit) charged to operations	275	800	805	1,900
Charge-offs	(419)	(938)	(1,158)	(2,299)
Recoveries	146	464	359	709
Balance at end of period	20,936	20,820	20,936	20,820
Ending allowance balance attributed to loans:
Individually evaluated for impairment	4,069		4,069		3,647
Collectively evaluated for impairment	16,867		16,867		17,283
Total ending allowance balance	20,936		20,936		20,930
Loans:
Loans individually evaluated for impairment	42,382		42,382		39,903
Loans collectively evaluated for impairment	1,623,291		1,623,291		1,531,676
Total loans	1,665,673		1,665,673		1,571,579
Residential Real Estate [Member]
Allowance for loan losses:
Balance at beginning of period	4,290	5,185	4,859	5,241
Provision (benefit) charged to operations	207	19	25	849
Charge-offs	(205)	(739)	(795)	(1,689)
Recoveries	105	435	308	499
Balance at end of period	4,397	4,900	4,397	4,900
Ending allowance balance attributed to loans:
Individually evaluated for impairment	131		131		2
Collectively evaluated for impairment	4,266		4,266		4,857
Total ending allowance balance	4,397		4,397		4,859
Loans:
Loans individually evaluated for impairment	18,856		18,856		18,192
Loans collectively evaluated for impairment	792,702		792,702		763,214
Total loans	811,558		811,558		781,406
Commercial Real Estate [Member]
Allowance for loan losses:
Balance at beginning of period	11,413	9,286	10,371	8,937
Provision (benefit) charged to operations	(337)	463	697	787
Recoveries	1	25	9	50
Balance at end of period	11,077	9,774	11,077	9,774
Ending allowance balance attributed to loans:
Individually evaluated for impairment	3,493		3,493		3,612
Collectively evaluated for impairment	7,584		7,584		6,759
Total ending allowance balance	11,077		11,077		10,371
Loans:
Loans individually evaluated for impairment	20,885		20,885		17,643
Loans collectively evaluated for impairment	556,176		556,176		511,302
Total loans	577,061		577,061		528,945
Consumer [Member]
Allowance for loan losses:
Balance at beginning of period	1,369	2,148	1,360	2,264
Provision (benefit) charged to operations	80	(13)	196	(107)
Charge-offs	(204)	(199)	(313)	(375)
Recoveries	39	3	41	157
Balance at end of period	1,284	1,939	1,284	1,939
Ending allowance balance attributed to loans:
Individually evaluated for impairment	445		445		33
Collectively evaluated for impairment	839		839		1,327
Total ending allowance balance	1,284		1,284		1,360
Loans:
Loans individually evaluated for impairment	2,365		2,365		2,961
Loans collectively evaluated for impairment	199,474		199,474		197,722
Total loans	201,839		201,839		200,683
Commercial and Industrial [Member]
Allowance for loan losses:
Balance at beginning of period	1,044	1,094	1,383	1,348
Provision (benefit) charged to operations	128	(2)	(171)	(23)
Charge-offs	(10)		(50)	(235)
Recoveries	1	1	1	3
Balance at end of period	1,163	1,093	1,163	1,093
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	1,163		1,163		1,383
Total ending allowance balance	1,163		1,163		1,383
Loans:
Loans individually evaluated for impairment	276		276		1,107
Loans collectively evaluated for impairment	74,939		74,939		59,438
Total loans	75,215		75,215		60,545
Unallocated [Member]
Allowance for loan losses:
Balance at beginning of period	2,818	2,781	2,957	2,720
Provision (benefit) charged to operations	197	333	58	394
Balance at end of period	3,015	3,114	3,015	3,114
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	3,015		3,015		2,957
Total ending allowance balance	$ 3,015		$ 3,015		$ 2,957