Earnings Per Share - Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerators:
Net income	$ 20,378	$ 16,375	$ 37,166	$ 30,195
Denominators:
Basic weighted average common shares outstanding	33,819,320	33,621,444	33,833,153	33,500,736
Dilutive effect of share based awards (in shares)	1,173,906	888,956	1,218,614	930,292
Diluted weighted average common shares outstanding	34,993,226	34,510,400	35,051,767	34,431,028
Earnings Per Share:
Basic (in dollars per share)	$ 0.60	$ 0.49	$ 1.10	$ 0.90
Diluted (in dollars per share)	$ 0.58	$ 0.47	$ 1.06	$ 0.88
Weighted average common shares considered anti-dilutive in computing diluted earnings per share	2,893	59,455	227,941	130,103