CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net Loss	$ (107,987)	$ (240,931)	$ (291,705)	$ (552,184)
Other Comprehensive (Loss) Income, Net of Tax
Currency translation adjustments	(1,170)	(105,727)	12,963	(63,738)
Defined benefit pension plan adjustments	624	1,069	847	2,685
Net unrealized losses on available-for-sale security	(1,944)	(2,709)	(67)	(2,789)
Net unrealized gains on derivative instruments:
Unrealized holding gains	3,254		9,072
Unrealized holding gains		17,652		12,333
Reclassification adjustment for realized (losses) gains included in net loss	(2,492)		(3,251)
Reclassification adjustment for realized (losses) gains included in net loss		4,786		9,217
Net unrealized gains on derivative instruments	762		5,821
Net unrealized gains on derivative instruments		22,438		21,550
Other Comprehensive (Loss) Income, Net of Tax	(1,728)	(84,929)	19,564	(42,292)
Comprehensive Loss	$ (109,715)	$ (325,860)	$ (272,141)	$ (594,476)