Debt (Details Textuals) (USD $)	6 Months Ended				6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 U.S. Commercial Paper [Member]	Dec. 31, 2010 U.S. Commercial Paper [Member]	Jun. 30, 2011 Medium-term Notes [Member]	May 31, 2011 350 million unsecured medium-term notes due June 2017 [Member]	Feb. 28, 2011 350 million unsecured medium-term notes due March 2015 [Member]	Feb. 28, 2011 Interest rate swaps maturing March 2015 [Member]	May 31, 2011 Interest rate swaps maturing June 2017 [Member]	Jun. 30, 2011 Letter of Credit [Member]	Jun. 30, 2011 Global Revolving Credit Facility [Member]	Jun. 30, 2011 Credit Facility Due on April 2012 [Member]
Debt (Textuals) [Abstract]
Commercial paper classified as long term debt			$ 531,900,000	$ 367,900,000
Repurchase price condition of notes					101% of Principal Plus Accrued And Unpaid Interest
Face amount of unsecured medium-term notes issued						350,000,000	350,000,000
Notional amount of interest rate swap	550,000,000	250,000,000				150,000,000	150,000,000	150,000,000	150,000,000
Line of Credit Facility [Line Items]
Maximum borrowing capacity under global revolving credit facility										75,000,000	900,000,000	875,000,000
Letter of credit outstanding amount										0
Unamortized original issue discounts	10,300,000	10,500,000
Notional amount of the executed interest rate swap designated as a fair value hedge	550,000,000	250,000,000				150,000,000	150,000,000	150,000,000	150,000,000
Number of lending institutions	12
Annual facility fees minimum	0.10%
Annual facility fees maximum	0.325%
Current annual facility fee	0.15%
Global revolving credit facility covenant terms, debt to consolidated tangible net worth ratio	less than or equal to 300%
Tangible net worth definition	Includes 50% of Deferred Federal Income Tax Liability and Excludes Intangibles
Debt to consolidated tangible net worth ratio	218.00%
Amount available under the global revolving credit facility	366,100,000
Total available proceeds under trade receivables purchase and sale program	175,000,000
Amount outstanding under trade receivables purchase and sale program	0	0
Letters of Credit and Surety Bonds Outstanding	$ 265,700,000	$ 264,800,000
Number of days under trade trade receivables purchase and sale program	364 days