Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Basic Earnings (Loss) per Share
Net Income (loss)	$ (170,914)	$ 6,420	$ (173,473)	$ 13,902	$ 23,991
Weighted-average common shares outstanding used in earnings per share computations (in shares)	61,606	62,398	61,773	62,606
Basic earnings per common share (in dollars per share)	$ (2.77)	$ 0.10	$ (2.81)	$ 0.22
Diluted Earnings (Loss) per Share
Net Income (loss)	$ (170,914)	$ 6,420	$ (173,473)	$ 13,902	$ 23,991
Shares used in diluted earnings per share computations (in shares)	61,606	62,585	61,773	62,818
Diluted earnings per common share (in dollars per share)	$ (2.77)	$ 0.10	$ (2.81)	$ 0.22
Computation of Shares Used in Earnings (Loss) Per Share Computations
Weighted-average common shares outstanding (in shares)	61,606	62,398	61,773	62,606
Weighted-average common equivalent shares - dilutive effect of stock options and awards (in shares)	0	187	0	212
Shares used in diluted earnings per share computations (in shares)	61,606	62,585	61,773	62,818