Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Assets
Federally-sponsored and corporate debt securities	$ 81.9	$ 159.8
Convertible Notes Due 2016
Liabilities
Convertible notes at carrying value		5.4
Recurring fair value measurements \| Level 1
Assets
Money market funds	662.3	496.4
Total assets	662.3	496.4
Liabilities
Convertible notes		16.0
Total liabilities		16.0
Recurring fair value measurements \| Level 2
Assets
Federally-sponsored and corporate debt securities	81.9	159.8
Total assets	81.9	159.8
Recurring fair value measurements \| Level 3
Liabilities
Contingent consideration	10.3	9.4
Total liabilities	10.3	9.4
Recurring fair value measurements \| Balance
Assets
Money market funds	662.3	496.4
Federally-sponsored and corporate debt securities	81.9	159.8
Total assets	744.2	656.2
Liabilities
Convertible notes		16.0
Contingent consideration	10.3	9.4
Total liabilities	$ 10.3	$ 25.4

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Carrying value as of the balance sheet date of the portion of long-term debt due within one year or the operating cycle if longer identified as Convertible Notes Payable. Convertible Notes Payable is a written promise to pay a note which can be exchanged for a specified amount of another, related security, at the option of the issuer and the holder.

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Fair value of investments in debt securities classified as held-to-maturity.

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Fair value of financial and nonfinancial obligations.

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Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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Fair value, as of the balance sheet date, of potential payments under the contingent consideration arrangement including cash and shares.

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