Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Consolidated Statements of Comprehensive Loss
Net Loss	$ (304,084)	$ (131,289)	$ (41,571)	$ (32,172)	$ (86,513)	$ (28,806)	$ (30,509)	$ (23,978)	$ (73,743)	$ (54,486)	$ (205,032)	$ (83,293)	$ (509,116)	$ (169,806)	$ (209,484)
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments		(2,325)	(2,288)	3,392	(2,566)	(2,492)	(879)	(268)	1,104	(1,147)	(1,221)	(3,639)	(906)	(6,204)	3,328
Unrealized pension actuarial gains (losses), net of tax		291	256	(224)	1,390	140	626	(403)	32	223	323	363	1,242	1,753	1,285
Total other comprehensive loss, net of tax		$ (133,323)	$ (43,603)	$ (29,004)	$ (87,689)	$ (31,158)	$ (30,762)	$ (24,649)	$ (72,607)	$ (55,410)	$ (205,930)	$ (86,569)	$ (508,780)	$ (174,257)	$ (204,871)