Debt 3.75% Convertible Senior Subordinated Notes (Details) (USD $)	12 Months Ended						3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 3.75% Convertible Senior Subordinated Notes, due 2025 [Member]	Dec. 31, 2011 3.75% Convertible Senior Subordinated Notes, due 2025 [Member]	Dec. 31, 2010 3.75% Convertible Senior Subordinated Notes, due 2025 [Member]	Jun. 30, 2012 3.75% Convertible Senior Subordinated Notes Due 2042 [Member]	Dec. 31, 2012 3.75% Convertible Senior Subordinated Notes Due 2042 [Member]
Debt Instrument, Face Amount				$ 575,000,000				$ 390,000,000
Debt Instrument, Interest Rate, Stated Percentage				3.75%				3.75%
Debt Instrument, Convertible, Conversion Price				$ 27.44				$ 41.50
Percent stock price closes above conversion price for option of conversion				130.00%
Deferred Finance Costs, Gross				9,400,000				3,600,000
Amortization of Financing Costs				400,000	600,000	100,000		100,000
Current Fiscal Year End Date	--12-31
Extinguishment of Debt, Amount				256,900,000
Write Off Of Deferred Debt Issuance Cost	12,466,000	6,012,000	6,636,000	3,800,000
Debt Related Costs							$ 33,300,000