Debt Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Long-term Debt, Gross	$ 2,464,064	$ 2,473,927
Debt Instrument, Unamortized Discount	450,018	462,274
7.75% Senior Subordinated Notes, Due 2020 [Member]
Long-term Debt, Gross	550,000	550,000
Long-term Debt, Fair Value	606,900	614,600
3.75% Convertible Senior Subordinated Notes, due 2025 [Member]
Long-term Debt, Gross	318,054	318,054
Long-term Debt, Fair Value	597,900	459,600
Long-term Debt	207,110	204,608
Debt Instrument, Unamortized Discount	110,944	113,446
4.00% Junior Subordinated Convertible Debentures, due 2033 [Member]
Long-term Debt, Gross	345,000	345,000
Long-term Debt, Fair Value	408,200	331,600
Long-term Debt	207,641	206,266
Debt Instrument, Unamortized Discount	137,359	138,734
3.25% Convertible Senior Debentures, Due 2035 [Member]
Long-term Debt, Gross	427,500	427,500
Long-term Debt, Fair Value	440,600	425,400
Long-term Debt	385,309	377,782
Debt Instrument, Unamortized Discount	42,191	49,718
3.75% Convertible Senior Subordinated Notes Due 2042 [Member]
Long-term Debt, Gross	390,000	390,000
Long-term Debt, Fair Value	487,100	397,100
Long-term Debt	230,476	229,624
Debt Instrument, Unamortized Discount	$ 159,524	$ 160,376