Accumulated Other Comprehensive Loss (Components of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (637,300)	$ (561,825)	$ (579,239)	$ (569,430)
Other comprehensive income (loss) before reclassifications	21,598	(28,372)	(41,414)	(23,778)
Amounts reclassified from AOCL	2,671	1,464	7,622	4,475
Other comprehensive income (loss)	24,269	(26,908)	(33,792)	(19,303)
Ending balance	(613,031)	(588,733)	(613,031)	(588,733)
Accumulated other comprehensive loss, accumulated net loss from net investment hedge	12,100	(9,300)	24,600	5,900
Foreign currency translation items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(507,633)	(443,828)	(441,407)	(447,925)
Other comprehensive income (loss) before reclassifications	25,204	(30,600)	(41,022)	(26,503)
Amounts reclassified from AOCL	0	0	0	0
Other comprehensive income (loss)	25,204	(30,600)	(41,022)	(26,503)
Ending balance	(482,429)	(474,428)	(482,429)	(474,428)
Pension and other post-retirement effects
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(129,094)	(117,244)	(137,161)	(120,647)
Other comprehensive income (loss) before reclassifications	(3,647)	2,184	(531)	2,576
Amounts reclassified from AOCL	2,671	1,464	7,622	4,475
Other comprehensive income (loss)	(976)	3,648	7,091	7,051
Ending balance	(130,070)	(113,596)	(130,070)	(113,596)
Cash flow hedging activity
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(573)	(753)	(671)	(858)
Other comprehensive income (loss) before reclassifications	41	44	139	149
Amounts reclassified from AOCL	0	0	0	0
Other comprehensive income (loss)	41	44	139	149
Ending balance	(532)	(709)	(532)	(709)
Non- controlling Interests
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income (loss)	(4)	(66)	772	599
Accumulated other comprehensive income (loss), foreign currency translation adjustment, net of tax	$ 5,800	$ 5,100	$ 5,800	$ 5,100	$ 5,900	$ (5,100)	$ 5,200	$ (4,500)