Debt Convertible Debt Details (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
3.75% Convertible Senior Subordinated Notes, due 2025 [Member]
Debt Instrument, Convertible, Carrying Amount of Equity Component	$ 27,230
Debt Instrument, Convertible, Remaining Discount Amortization Period	13 years
Debt Instrument, Interest Rate, Effective Percentage	8.25%
4.00% Junior Subordinated Convertible Debentures, due 2033 [Member]
Debt Instrument, Convertible, Carrying Amount of Equity Component	151,655
Debt Instrument, Convertible, Remaining Discount Amortization Period	20 years 6 months
Debt Instrument, Interest Rate, Effective Percentage	8.01%
3.25% Convertible Senior Debentures, Due 2035 [Member]
Debt Instrument, Convertible, Carrying Amount of Equity Component	245,433
Debt Instrument, Convertible, Remaining Discount Amortization Period	3 years
Debt Instrument, Interest Rate, Effective Percentage	7.63%
3.75% Convertible Senior Subordinated Notes Due 2042 [Member]
Debt Instrument, Convertible, Carrying Amount of Equity Component	$ 161,600
Debt Instrument, Convertible, Remaining Discount Amortization Period	29 years 3 months
Debt Instrument, Interest Rate, Effective Percentage	7.11%