Debt and Credit Facilities (Narrative) (Details) (USD $) Share data in Millions, unless otherwise specified				3 Months Ended		1 Months Ended				3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Four Year Revolving Credit Facility [Member]	Mar. 31, 2012 Three Year Revolving Credit Facility [Member]	Mar. 31, 2012 Five Year Revolving Credit Facility [Member]	Apr. 30, 2012 Exchangeable Senior Notes [Member]	Mar. 31, 2012 Exchangeable Senior Notes [Member]	Dec. 31, 2011 Exchangeable Senior Notes [Member]	Apr. 30, 2009 Exchangeable Senior Notes [Member]	Mar. 31, 2012 Debentures With Put Feature [Member]	Feb. 15, 2012 Debentures With Put Feature [Member]	Dec. 31, 2011 Debentures With Put Feature [Member]
Commercial Paper	$ 0	$ 0
Short-term borrowings and current maturities of long-term debt	765,600,000	763,300,000					344,000,000	341,200,000		343,600,000		343,600,000
Debt instrument, maturity date range, start										2027
Debt instrument, maturity date range, end										2028
Debentures with put option available to be exercised											37,200,000
Senior note issued									345,000,000
Stated interest rate for debt instruments									4.50%
Portion of convertible debt allocated to debt									305,000,000
Portion of convertible debt allocated to equity, gross									40,000,000
Portion of convertible debt allocated to equity, net of allocated fees									39,000,000
Principal repayment, Exchangeable Senior Notes						352,300,000
Interest Paid						7,800,000
Ordinary shares issued, shares, Exchangeable Senior Notes (in millions)						10.8
Line of credit facilities, amounts expired				1,000,000,000
Line of credit facility, amount outstanding	$ 2,000,000,000		$ 1,000,000,000		$ 1,000,000,000
Line of credit facility, expiration date				May 20, 2015	March 15, 2017