Net Income per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 11,950	$ 8,385	$ 33,051	$ 19,840
Less distributed and undistributed earnings allocated to participating securities	303	243	822	576
Net income allocated to common shares	$ 11,647	$ 8,142	$ 32,229	$ 19,264
Weighted average common shares outstanding (in shares)	24,030	24,650	24,502	24,747
Incremental shares from assumed conversions of common stock options (in shares)	6	2	7	5
Adjusted weighted average common shares outstanding (in shares)	24,036	24,652	24,509	24,752
Potentially dilutive securities not included in weighted average share calculation due to anti-dilutive effect (in shares)	0	16	0	5