Acquisition of Astex Therapeutics Limited (Details) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended	0 Months Ended	1 Months Ended		13 Months Ended		0 Months Ended
	Dec. 31, 2012	Jul. 20, 2011 ATL	Aug. 31, 2012 ATL	Feb. 29, 2012 ATL	Feb. 28, 2013 ATL	Dec. 31, 2012 ATL	Jul. 20, 2011 ATL Common Stock	Jul. 20, 2011 ATL Maximum	Jul. 20, 2011 ATL Minimum
Acquisition of Astex Therapeutics Limited
Shares issued to the securityholders of the acquired entity							32.4
Percentage of shares issued after giving effect to the acquisition		35.00%
Deferred consideration payable in stock, cash, or a combination of stock and cash		$ 30,000,000
Deferred consideration payable period								30 months
Amount of deferred consideration payment									15,000,000
Period in which minimum deferred consideration will be paid								18 months
Incremental borrowing rate to discount expected present value of future semi-annual installments of deferred consideration liability (as a percent)		5.00%
Installment of deferred consideration paid	12,272,000		2,300,000	10,000,000	2,900,000
Installment payable in January 2014						$ 14,800,000