Debt 3.25% Convertible Senior Debentures (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Gains (Losses) on Extinguishment of Debt	$ 69,381,000	$ 56,280,000	$ 47,558,000
Long-term Debt, Gross	2,346,488,000us-gaap_DebtInstrumentCarryingAmount	2,500,434,000us-gaap_DebtInstrumentCarryingAmount
3.25% Convertible Senior Debentures, Due 2035 [Member]
Amortization of Financing Costs	1,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.25%
Deferred Finance Costs, Gross	17,000,000
Total consideration to complete debt extinguishment			25,000,000
Percent threshold average share price after stated period to allow cash distribution	120.00%
Percent stock price closes above conversion price for option of conversion	130.00%
Gains (Losses) on Extinguishment of Debt			2,000,000
Long-term Debt, Gross		$ 427,500,000

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total consideration to complete debt extinguishment

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Amount of noncash expense included in interest expense to issue debt and obtain financing associated with the related debt instruments. Alternate captions include noncash interest expense.

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Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

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Contractual interest rate for funds borrowed, under the debt agreement.

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For an unclassified balance sheet, the amount as of the balance sheet date of capitalized costs associated with the issuance of debt instruments (for example, legal, accounting, underwriting, printing, and registration costs) that will be charged against earnings over the life of the debt instruments to which such costs pertain. Such amount is before the consideration of accumulated amortization.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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