Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 113,146	$ 23,183	$ 205,969	$ 19,298
Other comprehensive income/(loss)
Market value adjustments on interest rate swaps, net of tax	7,905	(8,121)	(30,475)	(41,415)
Reclassification adjustment for gain on terminated interest rate swap included in net income	0	0	0	(67)
Foreign currency translation adjustments	10,799	(13,529)	(1,211)	(9,007)
Supplemental benefit plans adjustments, net of tax	(76)	(149)	36	(448)
Total other comprehensive income/(loss)	18,628	(21,799)	(31,650)	(50,937)
Comprehensive income/(loss)	$ 131,774	$ 1,384	$ 174,319	$ (31,639)