Debt 6.75% Senior Subordinated Notes (Details) (USD $)	12 Months Ended				12 Months Ended			3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Convertible Senior Subordinated Notes [Member]	Dec. 31, 2011 Senior Subordinated Notes, Due 2013 [Member]	Dec. 31, 2010 Senior Subordinated Notes, Due 2013 [Member]	Dec. 31, 2011 Junior Subordinated Convertible Debentures [Member]	Dec. 31, 2010 3.25% Convertible Senior Debentures, Due 2035 [Member]	Dec. 31, 2010 3.25% Convertible Senior Debentures, Due 2035 [Member]	Dec. 31, 2011 3.25% Convertible Senior Debentures, Due 2035 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 575,000,000	$ 225,000,000					$ 977,500,000
Debt Instrument, Interest Rate, Stated Percentage				3.75%	6.75%		4.00%			3.25%
Early debt extinguishment fees						7,600,000
Write Off Of Deferred Debt Issuance Cost	6,012,000	6,636,000	0			2,100,000		4,600,000	4,600,000
Payments of Debt Extinguishment Costs					400,000				1,300,000
Cash Tax Benefit of Convertible Debt	10,400,000	30,300,000	28,500,000
Cumulative Cash Tax Benefit of Convertible Debt	158,000,000
Debt Instrument, Convertible, Carrying Amount of Equity Component	619,223,000	619,223,000
Debt Instrument Convertible Principal Amount	1,372,500,000	1,372,500,000
Debt Instrument, Unamortized Discount	(422,681,000)	(446,876,000)						81,663,000	81,663,000	67,701,000
Debt Instrument Convertible Carrying Amount Net	$ 949,819,000	$ 925,624,000
Debt Instrument, Convertible, Remaining Discount Amortization Period				14			21.5			4