(Loss) Earnings per Common Share - Reconciliation of Earnings Per Share Data (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
(Loss) income from operations used for basic earnings per share	$ (215,038)	$ (70,140)	$ (87,984)	$ (28,747)	$ (65,217)	$ (2,897)	$ 2,537	$ 41,027	$ (401,909)	$ (24,550)	$ 184,243
Convertible debt income adjustments, net of tax									0	0	1,049
(Loss) income from operations adjusted for convertible debt as used for diluted earnings per share									$ (401,909)	$ (24,550)	$ 185,292
(Loss) income from operations per share:
Basic (in Dollars per share)	$ (1.71)	$ (0.56)	$ (0.70)	$ (0.23)	$ (0.52)	$ (0.02)	$ 0.02	$ 0.33	$ (3.21)	$ (0.20)	$ 1.50
Diluted (in Dollars per share)	$ (1.71)	$ (0.56)	$ (0.70)	$ (0.23)	$ (0.52)	$ (0.02)	$ 0.02	$ 0.33	$ (3.21)	$ (0.20)	$ 1.47
Shares used in computing (loss) income per share:
Weighted average basic shares outstanding (in Shares)									125,383	124,790	122,869
Dilutive securities:
Stock options and unvested RSUs (in Shares)									0	0	914
Shares issuable on conversion of the Notes (in Shares)									0	0	2,018
Total dilutive securities (in Shares)									0	0	2,932
Weighted average diluted shares outstanding (in Shares)									125,383	124,790	125,801