Net Income per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 14,065	$ 11,950	$ 56,471	$ 33,051
Less distributed and undistributed earnings allocated to participating securities	330	303	1,283	822
Net income allocated to common shares	$ 13,735	$ 11,647	$ 55,188	$ 32,229
Weighted average common shares outstanding (in shares)	20,843	24,030	20,895	24,502
Incremental shares from assumed conversions of common stock options (in shares)	13	6	11	7
Adjusted weighted average common shares outstanding (in shares)	20,856	24,036	20,906	24,509