Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 186,057	$ 202,428	$ 199,140	$ 253,420	$ 283,667	$ 284,095	$ 280,734	$ 268,347	$ 841,045	$ 1,116,843	$ 985,076
Gross Profit	83,085	97,963	102,967	149,132	169,254	170,227	171,773	163,017	433,147	674,271	596,012
Operating (Loss) Income	(116,442)	9,423	14,530	74,833	60,796	86,828	92,368	87,579	(17,656)	327,571	294,611
Net (Loss) Income, Amount	$ (65,217)	$ (2,897)	$ 2,537	$ 41,027	$ 32,455	$ 47,909	$ 61,993	$ 41,886	$ (24,550)	$ 184,243	$ 150,798
Net (Loss) Income, Per Basic Share (in Dollars per share)	$ (0.52)	$ (0.02)	$ 0.02	$ 0.33	$ 0.26	$ 0.38	$ 0.51	$ 0.35	$ (0.20)	$ 1.50	$ 1.29
Net (Loss) Income, Per Diluted Share (in Dollars per share)	$ (0.52)	$ (0.02)	$ 0.02	$ 0.33	$ 0.26	$ 0.38	$ 0.50	$ 0.34	$ (0.20)	$ 1.47	$ 1.22