Consolidated Statement of Changes in Retained Earnings and Accumulated Other Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	$ 538,633
Net income	67,944	$ 87,927	$ 88,049
Pension and post-retirement plan adjustments, net of tax ($1,160, $26,840 and $30,849)	6,181	(48,490)	54,951
Loss attributable to noncontrolling interests	4,280	1,176	1,331
Balance at end of period	517,128	538,633
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	835,126	792,206	747,953
Net income	67,944	87,927	88,049
Loss attributable to noncontrolling interests	2,863	579	198
Common dividends	(47,338)	(45,544)	(43,952)
Preferred dividends	(42)	(42)	(42)
Balance at end of period	858,553	835,126	792,206
Accumulated Other Comprehensive (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	(166,730)	(78,269)	(127,072)
Foreign currency translation adjustments	(49,067)	(40,568)	(7,281)
Pension and post-retirement plan adjustments, net of tax ($1,160, $26,840 and $30,849)	6,181	(48,490)	54,951
Loss attributable to noncontrolling interests	1,417	597	1,133
Balance at end of period	$ (208,199)	$ (166,730)	$ (78,269)