Condensed Consolidated Statements of Comprehensive Income (Unaudited) Statement - 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)/income	$ (5,572)	$ 58,516	$ (3,885)	$ 86,803
Other comprehensive loss
Adoption of new accounting standards	0	0	0	408
Market value adjustments on interest rate swaps, net of tax	(21,088)	4,101	(33,294)	8,238
Reclassification adjustment for loss on terminated interest rate swap included in net loss	(67)	0	(67)	0
Foreign currency translation adjustments	(820)	(13,486)	4,522	(17,600)
Supplemental benefit plans adjustments, net of tax	(150)	(123)	(299)	(247)
Total other comprehensive loss	(22,125)	(9,508)	(29,138)	(9,201)
Comprehensive (loss)/income	$ (27,697)	$ 49,008	$ (33,023)	$ 77,602