Net Income per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 9,713	$ 7,314	$ 42,406	$ 21,101
Less distributed and undistributed earnings allocated to participating securities	229	179	962	521
Net income allocated to common shares	$ 9,484	$ 7,135	$ 41,444	$ 20,580
Weighted average common shares outstanding (in shares)	20,869	24,766	20,921	24,741
Incremental shares from assumed conversions of common stock options (in shares)	15	7	10	8
Adjusted weighted average common shares outstanding (in shares)	20,884	24,773	20,931	24,749