Earnings Per Share - Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerators:
Net income	$ 21,077	$ 16,050	$ 58,243	$ 46,245
Denominators:
Basic weighted average common shares outstanding	33,838,374	33,624,401	33,834,392	33,542,258
Dilutive effect of share based awards (in shares)	1,205,613	1,051,084	1,214,280	970,557
Diluted weighted average common shares outstanding	35,043,987	34,675,485	35,048,672	34,512,815
Earnings Per Share:
Basic (in dollars per share)	$ 0.62	$ 0.48	$ 1.72	$ 1.38
Diluted (in dollars per share)	$ 0.60	$ 0.46	$ 1.66	$ 1.34
Weighted average common shares considered anti-dilutive in computing diluted earnings per share	0	32,516	151,961	97,574