Consolidated Statement of Changes in Retained Earnings and Accumulated Other Comprehensive Loss Statement (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 572,347
Net income	22,495	24,391	36,412	43,786
Pension and post-retirement plan adjustments, net of tax of $1,629, $1,278, $2,434 and $2,556	2,882	2,107	4,300	4,214
Ending balance	598,102		598,102
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	795,051	756,867	792,206	747,953
Net income	22,495	24,391	36,412	43,786
(Income) loss attributable to noncontrolling interests	(7)	(342)	102	(451)
Common dividends	(11,310)	(11,151)	(22,481)	(21,513)
Preferred dividends	(10)	(10)	(20)	(20)
Ending balance	806,219	769,755	806,219	769,755
Accumulated Other Comprehensive (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(77,667)	(130,005)	(78,269)	(127,072)
Foreign currency translation adjustments	54	(7,638)	(904)	(13,226)
Pension and post-retirement plan adjustments, net of tax of $1,629, $1,278, $2,434 and $2,556	2,882	2,107	4,300	4,214
(Income) loss attributable to noncontrolling interests		373	142	921
Ending balance	$ (74,731)	$ (135,163)	$ (74,731)	$ (135,163)