Net Income Per Share (Details) (USD $) In Thousands, except Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Net Income per Share [Abstract]
Net income	$ 6,741	$ 5,118	$ 15,527	$ 7,417
Less income allocated to participating securities	(199)	(51)	(463)	(214)
Net income allocated to common shares	$ 6,542	$ 5,067	$ 15,064	$ 7,203
Weighted average common shares outstanding	25,726	25,381	25,608	25,231
Incremental shares from assumed conversions of common stock options	101	112	110	102
Adjusted weighted average common shares outstanding	25,827	25,493	25,718	25,333
Potentially dilutive securities not included in weighted average share calculation due to anti-dilutive effect	8	460	4	568