Earnings per Share - Computation of Basic Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income	$ 2,844	$ 2,599	$ 5,365	$ 5,329
Diluted EPS, Shares (Denominator)	3,277,729	3,276,122	3,277,516	3,276,100
Basic EPS, Shares (Denominator)	3,276,079	3,276,079	3,276,079	3,276,079
Diluted EPS, Per-share Amount	$ 0.87	$ 0.79	$ 1.64	$ 1.63
Basic EPS, Per-share Amount	$ 0.87	$ 0.79	$ 1.64	$ 1.63
Shares Includable [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Basic EPS, Per-share Amount
Income Available [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Basic EPS, Per-share Amount	$ 0.87	$ 0.79	$ 1.64	$ 1.63
Numerator [Member] | Shares Includable [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income
Numerator [Member] | Income Available [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income	$ 2,844	$ 2,599	$ 5,365	$ 5,329
Denominator [Member] | Shares Includable [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Basic EPS, Shares (Denominator)	1,650	43	1,437	21
Denominator [Member] | Income Available [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Basic EPS, Shares (Denominator)	3,276,079	3,276,079	3,276,079	3,276,079