Condensed Consolidated Statements of Comprehensive Income - 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	$ 16,964	$ 41,388	$ 147,138	$ 165,589
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	7,498	3,553	(15,066)	9,078
Interest rate swaps – net change in deferred gain or loss	4,379	(11,379)	(37,453)	(50,599)
Pension plans – net change in deferred actuarial loss	85	41	244	124
Other comprehensive income (loss), net of tax	11,962	(7,785)	(52,275)	(41,397)
Comprehensive income	$ 28,926	$ 33,603	$ 94,863	$ 124,192