Net Income Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Net Income Per Common Share
Number of outstanding options not included in computation of Diluted EPS (in shares)	0	6,000
Numerator
Net income	$ 34,786	$ 27,092
Denominator
Weighted average number of common shares outstanding	51,820,000	51,218,000
Effect of outstanding share-based awards	1,382,000	796,000
Weighted average number of shares for diluted net income per common share	53,202,000	52,014,000
Basic earnings per-share (in dollars per share)	$ 0.67	$ 0.53
Diluted earnings per-share (in dollars per share)	$ 0.65	$ 0.52