Consolidated Statement of Changes in Retained Earnings and Accumulated Other Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ 558,165
Net income	$ 32,226	$ 25,022	59,530	$ 69,026
Pension and post-retirement plan adjustments, net of tax of $1,046, $1,267, $3,132, and $4,161 for the three and nine months ended September 30, 2016 and September 30, 2015	2,180	1,893	6,321	5,679
Income attributable to noncontrolling interests	(4,289)	(1,021)	(3,185)	(3,271)
Ending Balance	616,739		616,739
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	896,621	877,103	901,415	858,553
Net income	32,226	25,022	59,530	69,026
Income attributable to noncontrolling interests	(160)	(836)	(519)	(2,006)
Common dividends	(13,366)	(12,381)	(39,170)	(36,645)
Preferred dividends	(10)	(10)	(30)	(30)
Cumulative effect of the adoption of ASU 2016-16 (Note 2)	(5,915)		(5,915)
Ending Balance	915,311	888,898	915,311	888,898
Accumulated Other Comprehensive (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(199,775)	(202,476)	(230,246)	(208,199)
Foreign currency translation adjustments	10,021	(2,411)	34,888	(3,519)
Pension and post-retirement plan adjustments, net of tax of $1,046, $1,267, $3,132, and $4,161 for the three and nine months ended September 30, 2016 and September 30, 2015	2,180	1,893	6,321	5,679
Income attributable to noncontrolling interests	(4,129)	(185)	(2,666)	(1,265)
Reclassification from accumulated other comprehensive (loss) into earnings				4,125
Ending Balance	$ (191,703)	$ (203,179)	$ (191,703)	$ (203,179)