v2.4.0.6
Long-Term Debt (Details) (USD $)
 9 Months Ended 9 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
6.50% Senior Notes [Member]
Dec. 31, 2011
6.50% Senior Notes [Member]
Sep. 30, 2012
6.625% Senior Notes [Member]
Dec. 31, 2011
6.625% Senior Notes [Member]
Sep. 30, 2012
Convertible Debt [Member]
Dec. 31, 2011
Convertible Debt [Member]
Sep. 30, 2012
6.50% Senior Notes due 2023 [Member]
Long-term debt                  
Debt Instrument, Face Amount     $ 350,000,000   $ 350,000,000       $ 400,000,000
Interest rate on notes (as a percent)     6.50% 6.50% 6.625% 6.625% 3.50% 3.50% 6.50%
Proceeds from Issuance of Long-term Debt 392,223,000 0             392,223,000
Stock Issued During Period, Shares, Conversion of Convertible Securities             864,106    
Cash Paid For Redemption Of Convertible Debt             6,200,000    
Repayments of Long-term Debt             281,300,000    
Deferred Finance Costs, Gross                 7,800,000
Debt Instrument Future Redemption Amount As Percentage Of Principal                 35.00%
Debt Instrument Future Redemption Price As Percentageof Principal First Through Third Year                 106.50%
Senior Notes due 2023 Redemption Schedule [Abstract]                  
Debt Instrument, Future Redemption Price as Percentage of Principal, Year 5                 103.25%
Debt Instrument Future Redemption Price as Percentage of Principal, Year 6                 102.167%
Debt Instrument, Future Redemption Price as Percentage of Principal, Year 7                 101.083%
Debt Instrument, Future Redemption Price as Percentage of Principal, Year 8 and Thereafter                 100.00%
Debt Instrument, Covenant Compliance, Dividends Excluded From Computation                 $ 6,500,000
Debt Instrument Future Redemption Price As Percentage Of Principal, First Five Year                 100.00%