Debt Schedule of Convertible Debt (Details) (USD $)	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 2,338,552,000us-gaap_DebtInstrumentCarryingAmount	$ 2,346,488,000us-gaap_DebtInstrumentCarryingAmount
Aggregate Principal of Convertible Debt, if Converted	386,000,000
3.75% Convertible Senior Subordinated Notes, due 2025 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	79,969,000	79,972,000
Debt Instrument, Convertible, Carrying Amount of Equity Component	6,913,000
Remaining amortization period for the debt discount (in years)	10 years 274 days
Debt Instrument, Interest Rate, Effective Percentage	8.25%
4.00% Junior Subordinated Convertible Debentures, due 2033 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	305,632,000	306,683,000
Debt Instrument, Convertible, Carrying Amount of Equity Component	117,942,000
Remaining amortization period for the debt discount (in years)	18 years 91 days
Debt Instrument, Interest Rate, Effective Percentage	8.01%
3.25% Convertible Senior Debentures, Due 2035 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	186,033,000	186,033,000
Debt Instrument, Convertible, Carrying Amount of Equity Component	233,901,000
Remaining amortization period for the debt discount (in years)	274 days
Debt Instrument, Interest Rate, Effective Percentage	7.63%
3.25% Convertible Senior Subordinated Exchange Debentures, due 2035 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	241,467,000	241,467,000
Debt Instrument, Convertible, Carrying Amount of Equity Component	25,259,000
Remaining amortization period for the debt discount (in years)	6 years
Debt Instrument, Interest Rate, Effective Percentage	5.24%
3.5% Convertible senior subordinated debt [Domain]
Debt Instrument [Line Items]
Long-term Debt, Gross	424,250,000	424,250,000
Debt Instrument, Convertible, Carrying Amount of Equity Component	$ 208,200,000
Remaining amortization period for the debt discount (in years)	28 years 329 days
Debt Instrument, Interest Rate, Effective Percentage	7.70%

Aggregate Principal of Convertible Debt, if Converted

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

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- Definition

The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6031897-161870

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- Definition

Remaining amortization period for discount on the liability component of convertible debt which may be settled in cash upon conversion, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (a)

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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-Name Accounting Standards Codification

-Topic 210

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-Section S99

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-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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