Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means 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. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

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Number of new stock issued during the period.

+ References+ Details

Nature of the Business (Details) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended	0 Months Ended
	Jun. 30, 2013 item	Jul. 17, 2013 Subsequent events	Jul. 17, 2013 Convertible senior notes Subsequent events
Nature of the Business
Number of novel therapeutic oncology candidates	6
Unrestricted cash and cash equivalents and available-for-sale securities	$ 62.1
Public Offering
Shares of common stock sold in underwritten public offering		5,750,000
Interest rate (as a percent)			4.50%
Notes issued			125.0
Net proceeds from sale of common stock and convertible senior notes		$ 147.4