Debt Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Long-term Debt, Gross	$ 2,545,511	$ 2,473,927
Debt Instrument, Unamortized Discount	594,090	462,274
7.75% Senior Subordinated Notes, Due 2020 [Member]
Long-term Debt, Gross	400,000	550,000
Long-term Debt, Fair Value	441,300	614,600
3.75% Convertible Senior Subordinated Notes, due 2025 [Member]
Long-term Debt, Gross	132,417	318,054
Long-term Debt, Fair Value	279,600	459,600
Long-term Debt	86,769	204,608
Debt Instrument, Unamortized Discount	45,648	113,446
4.00% Junior Subordinated Convertible Debentures, due 2033 [Member]
Long-term Debt, Gross	345,000	345,000
Long-term Debt, Fair Value	470,800	331,600
Long-term Debt	208,349	206,266
Debt Instrument, Unamortized Discount	136,651	138,734
3.25% Convertible Senior Debentures, Due 2035 [Member]
Long-term Debt, Gross	427,500	427,500
Long-term Debt, Fair Value	453,200	425,400
Long-term Debt	389,180	377,782
Debt Instrument, Unamortized Discount	38,320	49,718
3.75% Convertible Senior Subordinated Notes Due 2042 [Member]
Long-term Debt, Gross	390,000	390,000
Long-term Debt, Fair Value	549,700	397,100
Long-term Debt	224,572	229,624
Debt Instrument, Unamortized Discount	165,428	160,376
3.50% Convertible Senior Subordianted Notes, Due 2044 [Member]
Long-term Debt, Gross	424,250	0
Long-term Debt, Fair Value	403,000	0
Long-term Debt	216,207	0
Debt Instrument, Unamortized Discount	$ 208,043	$ 0