Consolidated Statement of Changes in Retained Earnings and Accumulated Other Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ 516,496
Net income	$ 31,931	$ 23,845	44,004	$ 33,295
Pension and post-retirement plan adjustments, net of tax of $1,042, $1,477, $2,086, and $2,894 for the three and six months ended June 30, 2016 and June 30, 2015	1,894	2,623	3,786	5,152
(Income) loss attributable to noncontrolling interests	(2,252)	649	(2,250)	1,139
Ending Balance	550,305		550,305
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	858,368	833,255	858,553	835,126
Net income	31,931	23,845	44,004	33,295
(Income) loss attributable to noncontrolling interests	(848)	453	(1,170)	685
Common dividends	(12,338)	(11,959)	(24,264)	(23,502)
Preferred dividends	(10)	(10)	(20)	(20)
Ending Balance	877,103	845,584	877,103	845,584
Accumulated Other Comprehensive (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(190,580)	(187,993)	(208,199)	(166,730)
Foreign currency translation adjustments	(15,056)	3,891	(1,108)	(20,159)
Pension and post-retirement plan adjustments, net of tax of $1,042, $1,477, $2,086, and $2,894 for the three and six months ended June 30, 2016 and June 30, 2015	1,894	2,623	3,786	5,152
(Income) loss attributable to noncontrolling interests	(756)	196	(1,080)	454
Reclassification from accumulated other comprehensive (loss) into earnings	2,022		4,125
Ending Balance	$ (202,476)	$ (181,283)	$ (202,476)	$ (181,283)