Net Income per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Numerator:
Net income	$ 2,745	$ 3,893	$ 13,536	$ 13,866
Adjustment for interest expense on convertible notes	96	33	304	33
Net income, as adjusted	$ 2,841	$ 3,926	$ 13,840	$ 13,899
Denominator:
Weighted average number of shares of Common Stock outstanding	6,877,915	6,831,048	6,863,564	6,821,944
Weighted average effect of dilutive stock options	128,611	167,770	155,360	160,235
Weighted average effect of assumed conversion of convertible notes	427,396	203,568	427,912	68,602
Weighted average number of shares of Common Stock outstanding, as adjusted	7,433,922	7,202,386	7,446,836	7,050,781
Net income per common share:
Net income per common share - Basic	$ 0.40	$ 0.57	$ 1.97	$ 2.03
Net income per common share - Diluted	$ 0.38	$ 0.55	$ 1.86	$ 1.97