Net Income per Share (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]
Net income	$ 1,891	$ 3,488	$ 11,455	$ 16,661
Less distributed and undistributed earnings allocated to participating securities	(139)	(124)	(333)	(481)
Net income allocated to common shares	$ 1,752	$ 3,364	$ 11,122	$ 16,180
Weighted average common shares outstanding (in shares)	24,770	24,820	24,797	24,858
Incremental shares from assumed conversions of common stock options (in shares)	4	24	5	27
Adjusted weighted average common shares outstanding (in shares)	24,774	24,844	24,802	24,885
Potentially dilutive securities not included in weighted average share calculation due to anti-dilutive effect (in shares)	0	16	0	16