Debt Schedule of Convertible Debt (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 30, 2014
3.75% Convertible Senior Subordinated Notes, due 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Carrying Amount of Equity Component	$ 6,913
Remaining amortization period for the debt discount (in years)	11 years 183 days
Debt Instrument, Interest Rate, Effective Percentage	8.25%
4.00% Junior Subordinated Convertible Debentures, due 2033 [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Carrying Amount of Equity Component	118,348
Remaining amortization period for the debt discount (in years)	19 years
Debt Instrument, Interest Rate, Effective Percentage	8.01%
3.25% Convertible Senior Debentures, Due 2035 [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Carrying Amount of Equity Component	245,433
Remaining amortization period for the debt discount (in years)	1 year 183 days
Debt Instrument, Interest Rate, Effective Percentage	7.63%
3.75% Convertible Senior Subordinated Notes Due 2042 [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Carrying Amount of Equity Component	167,941
Remaining amortization period for the debt discount (in years)	27 years 274 days
Debt Instrument, Interest Rate, Effective Percentage	7.30%
3.5% Convertible senior subordinated debt [Domain]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Carrying Amount of Equity Component	$ 208,200
Remaining amortization period for the debt discount (in years)	29 years 237 days
Debt Instrument, Interest Rate, Effective Percentage	7.70%

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

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)

-URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6031898-161870

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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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 3: 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(a)(1))

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

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