Shareholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent, Period Start	$ 1,323,073	$ 1,251,582	$ 1,251,582
Net Income	53,437	58,412	276,005
Dividends	(48,985)		(186,828)
Issuance of shares under incentive stock plans	2,061		13,451
Stock-based compensation	6,466		16,181
Excess tax benefit on stock-based compensation	3,946		5,681
Repurchase of common shares	(7,783)		(7,909)
Net gain (loss) from pension and postretirement plans	3,140	2,093	(46,263)
Foreign currency translation adjustment	5,825	288	3,546
Joint venture cash flow hedges	1,205	(567)	(2,373)
Stockholders' Equity Attributable to Parent, Period End	1,342,385		1,323,073
Dividends [Abstract]
Common Stock, Dividends, Per Share, Declared	$ 0.40	$ 0.36	$ 1.52
Common Stock Including Additional Paid in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent, Period Start	630,286	602,882	602,882
Shares Issued, Period Start	122,035,177	121,023,140	121,023,140
Issuance of shares under incentive stock plans	2,061		13,451
Issuance of shares under incentive stock plan, Shares	585,351		1,220,731
Stock-based compensation	6,466		16,181
Excess tax benefit on stock-based compensation	3,946		5,681
Repurchase of common shares	(7,783)		(7,909)
Stock Repurchased During Period, Shares	(169,757)		(208,694)
Shares Issued, Period End	122,450,771		122,035,177
Stockholders' Equity Attributable to Parent, Period End	634,976		630,286
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent, Period Start	806,235	717,058	717,058
Net Income	53,437		276,005
Dividends	(48,985)		(186,828)
Stockholders' Equity Attributable to Parent, Period End	810,687		806,235
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent, Period Start	(113,448)	(68,358)	(68,358)
Net gain (loss) from pension and postretirement plans	3,140		(46,263)
Foreign currency translation adjustment	5,825		3,546
Joint venture cash flow hedges	1,205		(2,373)
Stockholders' Equity Attributable to Parent, Period End	$ (103,278)		$ (113,448)