Other Comprehensive Income - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (327,273)	$ (314,986)	$ (323,673)	$ (302,414)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(7,689)	1,170
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(12,233)	(19,177)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	16,322	5,435
Other Comprehensive Income (Loss), Net of Tax	(3,600)	(12,572)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(61,586)	(85,767)	(61,015)	(63,913)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(571)	(21,854)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Other Comprehensive Income (Loss), Net of Tax	(571)	(21,854)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(3,387)	(1,714)	(1,222)	702
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(7,689)	1,170
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	5,524	(3,586)
Other Comprehensive Income (Loss), Net of Tax	(2,165)	(2,416)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(262,300)	(227,505)	$ (261,436)	$ (239,203)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(11,662)	2,677
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	10,798	9,021
Other Comprehensive Income (Loss), Net of Tax	$ (864)	$ 11,698