Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	6 Months Ended		12 Months Ended
	Jun. 30, 2013		Dec. 31, 2012		Jun. 30, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate loans pledged to secured borrowings obtained from Federal Home Loan Bank	$ 216,000,000		$ 162,000,000
Decrease in total past due loans	1,200,000
Total past due loans	12,257,000		13,535,000
Decrease of Loans past due for 90 days or more	7,900,000
Loans past due 90 days or more	2,873,000		10,799,000
Nonaccrual loans	8,725,000		17,655,000
Loan foreclosure	5,600,000
Impairment write-downs	1,800,000
Gross loans	729,216,000		730,599,000		708,398,000
Increase (Decrease) in loan portfolios	(1,383,000)
Total impaired loans	31,085,000		39,251,000
Decrease in impaired loans	8,200,000
Allocated specific reserves required on modified TDR	2,200,000
Troubled debt restructurings	27,232,000		27,232,000
Impaired loans with no specific reserves	26,800,000		34,900,000
Investment in impaired loans	36,600,000		34,800,000
Interest that would have been earned had impaired loans remained current in accordance with original terms	325,000
Accruing TDR's	22,360,000	[1]	21,596,000	[1]
TDR's covered with specific reserve	4,300,000
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due loans	5,348,000		6,394,000
Loans past due 90 days or more	756,000		4,295,000
Loans 30 - 89 days past due	4,300,000
Nonaccrual loans	3,595,000		6,846,000
Gross loans	195,439,000		170,792,000		173,637,000
Net transfers of loan	5,600,000
Total impaired loans	11,867,000		16,180,000
Investment in impaired loans	13,824,000		14,709,000
Deemed Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired loans with no specific reserves	30,700,000
Borrower one
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total impaired loans	5,600,000
Borrower two
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total impaired loans	2,900,000
Loans to 30 - 89 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increased in past due loans	6,600,000
Loans 30 - 89 days past due	9,400,000		2,700,000
TDR Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings	4,300,000
Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	674,373,000		673,656,000
Increase (Decrease) in loan portfolios	717,000
Net transfers of loan	5,100,000
Pass | Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	173,199,000		146,952,000
Increase (Decrease) in loan portfolios	26,247,000
Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	5,302,000		15,804,000
Increase (Decrease) in loan portfolios	(10,502,000)
Special Mention | Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	217,000		2,381,000
Increase (Decrease) in loan portfolios	(2,164,000)
Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	48,565,000		41,027,000
Increase (Decrease) in loan portfolios	7,538,000
Net transfers of loan	2,300,000
Substandard | Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	21,047,000		21,347,000
Increase (Decrease) in loan portfolios	(300,000)
Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allocated specific reserves required on modified TDR	3,300,000
Troubled debt restructurings	33,000,000		21,595,000
Accruing TDR's	22,400,000
Performing | Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings	8,273,000		9,334,000
Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allocated specific reserves required on modified TDR	1,000,000
Troubled debt restructurings	4,879,000		5,637,000
Accruing TDR's	4,900,000
Nonperforming | Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings	2,599,000		1,753,000
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loan transfer into OREO	5,600,000
Charge offs loans	1,500,000
Loans 30 - 89 days past due	4,800,000
Commercial real estate loan, past due amount	2,000,000
Commercial real estate | Owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due loans			3,232,000
Loans past due 90 days or more			3,232,000
Nonaccrual loans	1,811,000		3,232,000
Gross loans	156,215,000		165,922,000
Total impaired loans	3,205,000		4,644,000
Investment in impaired loans	4,365,000		5,584,000
Commercial real estate | Pass | Owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	152,691,000		162,689,000
Increase (Decrease) in loan portfolios	(9,998,000)
Commercial real estate | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (Decrease) in loan portfolios	9,500,000
Commercial real estate | Substandard | Owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	3,523,000		3,232,000
Increase (Decrease) in loan portfolios	291,000
Commercial real estate | Nonperforming | Owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings	1,811,000
Consumer relationship | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (Decrease) in loan portfolios	1,100,000
Residential mortgage loans | Single-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due loans			996,000
Loans past due 90 days or more			359,000
Nonaccrual loans	788,000		839,000
Gross loans	75,241,000		87,263,000
Total impaired loans	788,000		839,000
Investment in impaired loans	812,000		1,050,000
Residential mortgage loans | Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	97,383,000		105,119,000
Investment in impaired loans			45,000
Residential mortgage loans | Pass | Single-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	73,264,000		84,237,000
Increase (Decrease) in loan portfolios	(10,973,000)
Residential mortgage loans | Pass | Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	97,383,000		104,747,000
Increase (Decrease) in loan portfolios	(7,364,000)
Residential mortgage loans | Special Mention | Single-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans			990,000
Increase (Decrease) in loan portfolios	(990,000)
Residential mortgage loans | Special Mention | Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans			373,000
Increase (Decrease) in loan portfolios	(373,000)
Residential mortgage loans | Substandard | Single-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,978,000		2,036,000
Increase (Decrease) in loan portfolios	(58,000)
Residential mortgage loans | Nonperforming | Single-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings	$ 55,000		$ 59,000

[1] See "Trouble Debt Restructurings" below for a description of accruing restructured loans at June 30, 2013 and December 31, 2012.