Net Income Per Share (Details) (USD $) In Thousands, except Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Earnings Per Share [Abstract]
Net income	$ 4,099	$ 7,234	$ 19,626	$ 14,651
Less income allocated to participating securities	(120)	(214)	(582)	(428)
Net income allocated to common shares	$ 3,979	$ 7,020	$ 19,044	$ 14,223
Weighted average common shares outstanding	25,425	25,312	25,546	25,258
Incremental shares from assumed conversions of common stock options (in shares)	74	111	98	105
Adjusted weighted average common shares outstanding (in shares)	25,499	25,423	25,644	25,363
Potentially dilutive securities not included in weighted average share calculation due to anti-dilutive effect (in shares)	54	339	21	492