Debt and Credit Facilities (Narrative) (Details) (USD $)				1 Months Ended	9 Months Ended		1 Months Ended		1 Months Ended
	Sep. 30, 2011	Dec. 31, 2010	Dec. 31, 2001	Apr. 30, 2009 Exchangeable Senior Notes [Member]	Sep. 30, 2011 Debentures With Put Feature [Member]	Feb. 15, 2011 Debentures With Put Feature [Member]	May 31, 2013 Four Year Revolving Credit Facility [Member]	Sep. 30, 2011 Four Year Revolving Credit Facility [Member]	May 31, 2015 Three Year Revolving Credit Facility [Member]	Jun. 30, 2011 Three Year Revolving Credit Facility [Member]	Sep. 30, 2011 Three Year Revolving Credit Facility [Member]
Long-term debenture with fixed interest rate					$ 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			11.00%	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
Fair value of debt	4,156,500,000	4,131,800,000
Line of credit facility, amount outstanding	2,000,000,000							1,000,000,000			1,000,000,000
Line of credit facilities, amounts expired											$ 1,000,000,000
Line of Credit Facility, Expiration Date							May 2013		May 2015	June 2011