Financial Instruments (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Derivative [Line Items]
Notional value of forward currency and option contracts	$ 108,700,000	$ 205,200,000
Fair value of commercial paper borrowings	330,500,000	304,500,000
Line of credit facility, borrowing capacity	600,000,000
Line of credit facility, years	5
Line of credit facility, expiration date	October 2016
Interest bearing bonds, maturity in years	thirty
Interest Rate Swap Contract [Member]
Derivative [Line Items]
Fixed-rate notes interest percentage	2.875%
Fixed-rate notes due date	2016
Notional value of interest rate swap contract	250,000,000
Fair value of long-term debt	$ 1,000,000,000	$ 1,000,000,000