Debt Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Long-term Debt, Gross	$ 2,426,257	$ 2,500,434
Debt Instrument, Unamortized Discount	537,115	573,082
7.75% Senior Subordinated Notes, Due 2020 [Member]
Long-term Debt, Gross	400,000	400,000
Long-term Debt, Fair Value	421,000	435,800
3.75% Convertible Senior Subordinated Notes, due 2025 [Member]
Long-term Debt, Gross	79,979	132,408
Long-term Debt, Fair Value	180,800	306,500
Long-term Debt	53,801	87,310
Debt Instrument, Unamortized Discount	26,178	45,098
4.00% Junior Subordinated Convertible Debentures, due 2033 [Member]
Long-term Debt, Gross	307,122	307,153
Long-term Debt, Fair Value	468,300	455,900
Long-term Debt	188,124	186,136
Debt Instrument, Unamortized Discount	118,998	121,017
3.25% Convertible Senior Debentures, Due 2035 [Member]
Long-term Debt, Gross	427,500	427,500
Long-term Debt, Fair Value	450,000	457,400
Long-term Debt	405,419	393,126
Debt Instrument, Unamortized Discount	22,081	34,374
3.75% Convertible Senior Subordinated Notes Due 2042 [Member]
Long-term Debt, Gross	390,000	390,000
Long-term Debt, Fair Value	608,000	592,800
Long-term Debt	226,389	225,014
Debt Instrument, Unamortized Discount	163,611	164,986
3.50% Convertible Senior Subordianted Notes, Due 2044 [Member]
Long-term Debt, Gross	424,250	424,250
Long-term Debt, Fair Value	469,600	428,500
Long-term Debt	218,003	216,643
Debt Instrument, Unamortized Discount	$ 206,247	$ 207,607