CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 152,530	$ 237,841	$ 245,713
Foreign currency:
Foreign currency translation continuing operations adjustments, net of tax of ($29,448), $10,977, and $24,150, respectively	173,074	(69,162)	(110,671)
Foreign currency translation, net of tax	173,074	(69,162)	(110,671)
Pension and other postretirement benefits plans:
Prior service cost recognized in net periodic cost, net of tax of $(39), $(20), and $0 respectively	66	36	0
Unamortized (loss) gain arising during the period, net of tax of $1,677, $1,849, and $1,469, respectively	(5,419)	(3,255)	(2,137)
Plan amendments, net of tax of $74, $0, and $0 respectively	(223)	0	0
Net loss recognized in net periodic cost, net of tax of $(2,457), $(2,489), and $(2,242), respectively	4,447	4,476	4,133
Foreign currency translation, net of tax of $413, $(373), and $(316), respectively	(1,083)	1,034	861
Pension and other postretirement benefits plans adjustment, net of tax	(2,212)	2,291	2,857
Derivatives qualifying as hedges:
Unrealized gain (loss) on derivatives arising during the period, net of tax $(631), $1,359, and $379, respectively	2,775	(3,434)	(2,974)
Reclassification adjustment on derivatives included in net income, net of tax of $83, $(1,010), and $(196), respectively	(11)	3,501	483
Derivatives qualifying as hedges, net of tax	2,764	67	(2,491)
Other comprehensive (loss) income, net of tax	173,626	(66,804)	(110,305)
Comprehensive income	326,156	171,037	135,408
Less: comprehensive income attributable to noncontrolling interest	0	421	774
Comprehensive income attributable to common shareholders	$ 326,156	$ 170,616	$ 134,634