Cash Convertible Senior Notes and Related Transactions (Details) (USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010	Mar. 31, 2010
Principal amount carrying amount and interest expense of notes
Aggregate principal amount of notes	$ 175.0		$ 175.0		$ 175.0	$ 175.0
Less: unamortized issuance discount	(30.4)		(30.4)		(33.6)
Carrying amount, net of discount	144.6		144.6		141.4
Contractual coupon interest	1.9	1.9	3.9	2.0
Amortization of discount and deferred financing costs	1.9	1.8	3.8	1.8
Total interest expense	$ 3.8	$ 3.7	$ 7.7	$ 3.8

Amortization of discount and deferred financing costs.

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Principal amount carrying amount and interest expense of notes.

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Including the current and noncurrent portions, carrying amount of debt identified as being convertible into another form of financial instrument (typically the entity's common stock) as of the balance sheet date, which originally required full repayment more than twelve months after issuance or greater than the normal operating cycle of the company.

+ References

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- Definition

Interest expense related to convertible debt instruments which has been recognized for the period, including the contractual interest coupon and amortization of the debt discount, if any.

+ References

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-Publisher FASB
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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

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-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
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The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

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-Publisher FASB
-Name FASB Staff Position (FSP)
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-Publisher AICPA
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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

+ References

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-Publisher SEC
-Name Regulation S-X (SX)
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