Consolidated Statement of Changes in Retained Earnings and Accumulated Other Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ 516,496
Net income	$ 25,022	$ 15,586	69,026	$ 48,881
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	1,893	2,294	5,679	7,446
(Income) loss attributable to noncontrolling interests	(1,021)	960	(3,271)	2,099
Ending Balance	564,193		564,193
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	877,103	845,584	858,553	835,126
Net income	25,022	15,586	69,026	48,881
(Income) loss attributable to noncontrolling interests	(836)	390	(2,006)	1,075
Common dividends	(12,381)	(11,916)	(36,645)	(35,418)
Preferred dividends	(10)	(10)	(30)	(30)
Ending Balance	888,898	849,634	888,898	849,634
Accumulated Other Comprehensive (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(202,476)	(181,283)	(208,199)	(166,730)
Foreign currency translation adjustments	(2,411)	(13,701)	(3,519)	(33,860)
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	1,893	2,294	5,679	7,446
(Income) loss attributable to noncontrolling interests	(185)	570	(1,265)	1,024
Reclassification from accumulated other comprehensive (loss) into earnings			4,125
Ending Balance	$ (203,179)	$ (192,120)	$ (203,179)	$ (192,120)