Debt 3.75% Convertible Senior Subordinated Notes (Details) (Convertible Senior Subordinated Notes [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010
Convertible Senior Subordinated Notes [Member]
Debt Instrument, Face Amount	$ 575.0
Debt Instrument, Interest Rate, Stated Percentage	3.75%
Percent stock price closes above conversion price for option of conversion	130.00%
Deferred Finance Costs, Gross	9.4
Amortization of Financing Costs	$ 0.6	$ 0.1

percent stock price closes above conversion price for option of conversion

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- Definition

The component of interest expense comprised of the periodic charge against earnings over the life of the financing arrangement to which such costs relate. Alternate captions include Noncash Interest Expense.

+ References

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-Name Regulation S-X (SX)

-Number 210

-Article 5

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- Definition

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

+ References

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

Interest rate stated in the contractual debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-Publisher FASB

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- Definition

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.

+ References

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

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-Topic 835

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