Net Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net Income (Loss) Per Common Share
Number of outstanding options not included in computation of Diluted EPS (in shares)	0	2,942,000	672,871	3,055,000
Numerator
Net Income	$ 36,268	$ 41,338	$ 77,363	$ 3,713
Denominator
Weighted average number of common shares outstanding	50,616,000	51,322,000	51,143,000	51,324,000
Effect of outstanding share-based awards	666,000	714,000	739,000	238,000
Weighted average number of shares for diluted net income per common share	51,282,000	52,036,000	51,882,000	51,562,000
Basic earnings per share (in dollars per share)	$ 0.72	$ 0.81	$ 1.51	$ 0.07
Diluted earnings per share (in dollars per share)	$ 0.71	$ 0.79	$ 1.49	$ 0.07