Earnings per Share (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Numerator:
Net income	$ 15,876,000	$ 18,541,000	$ 19,611,000
Denominator:
Weighted average shares of common stock outstanding	13,721,997	13,965,018	14,082,213
Effect of dilutive common stock equivalents	$ 17,827	$ 233,477	$ 490,708
Weighted average diluted common shares outstanding	13,739,824	14,198,495	14,572,921
EPS:
Basic	$ 1.16	$ 1.33	$ 1.39
Diluted	$ 1.16	$ 1.31	$ 1.35