Earnings (Loss) per Common Share - Reconciliation of Earnings Per Share Data (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
(Loss) income from continuing operations used for basic earnings per share	$ (24,550)	$ 184,243	$ 150,798
Convertible debt income adjustments, net of tax	0	1,049	3,222
(Loss) income from continuing operations adjusted for convertible debt as used for diluted earnings per share	$ (24,550)	$ 185,292	$ 154,020
(Loss) income from continuing operations per share:
Basic (in Dollars per share)	$ (0.20)	$ 1.50	$ 1.29
Diluted (in Dollars per share)	$ (0.20)	$ 1.47	$ 1.22
Shares used in computing (loss) income per share:
Weighted average basic shares outstanding (in Shares)	124,790	122,869	116,980
Dilutive securities:
Stock options and unvested RSUs (in Shares)	0	914	1,667
Stock warrants (in Shares)	0	0	0
Shares issuable on conversion of the Notes (in Shares)	0	2,018	7,115
Total dilutive securities (in Shares)	0	2,932	8,782
Weighted average diluted shares outstanding (in Shares)	124,790	125,801	125,762