Accumulated Other Comprehensive Loss - Amounts Included in Accumulated Other Comprehensive Loss, Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			$ 1,023,322
Other comprehensive loss before reclassifications			(19,543)
Amounts reclassified from accumulated other comprehensive loss			6,933
Other comprehensive income (loss)	$ 25,008	$ (22,550)	(12,610)	$ (19,115)
Ending balance	1,218,863	968,530	1,218,863	968,530
Accumulated Other Comprehensive Loss
Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(297,360)	(265,373)	(259,742)	(268,808)
Ending balance	(272,352)	$ (287,923)	(272,352)	$ (287,923)
Unrecognized Net Defined Benefit Plan Costs
Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(139,102)
Other comprehensive loss before reclassifications			(872)
Amounts reclassified from accumulated other comprehensive loss			5,427
Other comprehensive income (loss)			4,555
Ending balance	(134,547)		(134,547)
Change in Fair Value of Derivatives
Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(3,182)
Other comprehensive loss before reclassifications			(3,176)
Amounts reclassified from accumulated other comprehensive loss			1,506
Other comprehensive income (loss)			(1,670)
Ending balance	(4,852)		(4,852)
Foreign Currency Translation
Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(117,458)
Other comprehensive loss before reclassifications			(15,495)
Amounts reclassified from accumulated other comprehensive loss			0
Other comprehensive income (loss)			(15,495)
Ending balance	$ (132,953)		$ (132,953)