Debt Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Long-term Debt, Gross	$ 2,468,154	$ 2,473,927
Debt Instrument, Unamortized Discount	456,205	462,274
7.75% Senior Subordinated Notes, Due 2020 [Member]
Long-term Debt, Gross	550,000	550,000
Long-term Debt, Fair Value	613,300	614,600
3.75% Convertible Senior Subordinated Notes, due 2025 [Member]
Long-term Debt, Gross	318,054	318,054
Long-term Debt, Fair Value	512,100	459,600
Long-term Debt	205,846	204,608
Debt Instrument, Unamortized Discount	112,208	113,446
4.00% Junior Subordinated Convertible Debentures, due 2033 [Member]
Long-term Debt, Gross	345,000	345,000
Long-term Debt, Fair Value	355,300	331,600
Long-term Debt	206,947	206,266
Debt Instrument, Unamortized Discount	138,053	138,734
3.25% Convertible Senior Debentures, Due 2035 [Member]
Long-term Debt, Gross	427,500	427,500
Long-term Debt, Fair Value	430,200	425,400
Long-term Debt	381,510	377,782
Debt Instrument, Unamortized Discount	45,990	49,718
3.75% Convertible Senior Subordinated Notes Due 2042 [Member]
Long-term Debt, Gross	390,000	390,000
Long-term Debt, Fair Value	434,900	397,100
Long-term Debt	230,046	229,624
Debt Instrument, Unamortized Discount	$ 159,954	$ 160,376