Collaboration and License Agreements (Details Textual) In Millions, except Share data, unless otherwise specified					1 Months Ended		3 Months Ended		1 Months Ended		3 Months Ended	12 Months Ended
	Mar. 31, 2013 EUR (€)	Mar. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Mar. 31, 2013 March 31 2013 exchange rate [Member] USD ($)	Jun. 30, 2010 Merck KGaA [Member]	Feb. 29, 2008 Merck KGaA [Member] USD ($)	Mar. 31, 2013 Merck KGaA [Member] EUR (€) Installment	Mar. 31, 2013 Merck KGaA [Member] USD ($)	Nov. 30, 2011 Merck KGaA [Member] November 30, 2011 exchange rate [Member] USD ($)	Dec. 31, 2006 Merck Sharp [Member] USD ($)	Mar. 31, 2013 Merck Sharp [Member] USD ($)	Dec. 31, 2010 Merck Sharp [Member]
Collaboration and License Agreements (Textual) [Abstract]
License fee paid to company						$ 40.0				$ 20.0
Proceeds from the sale of common stock under Stock Purchase Agreement										10.0
Common stock price per share		$ 1.73	$ 1.05							$ 5.50
Aggregate potential milestones to be received under collaboration - one											165.0
Aggregate potential milestones to be received under collaboration - two											260.0
Research collaboration agreement, period										2 years
Extended revenue recognition period												2 years
Revenue Recognition Period												4 years
Maximum cumulative milestone revenue recognized in relation to the initiation of clinical trials or the achievement of preclinical milestones								12.1			1.0
Shares of common stock issued under stock purchase agreement										1,818,182
License fee received after foreign currency exchange rate in effect by company						39.7
Period of upfront payment revenue recognition					28 months
Number of monthly installments							10
Final monthly installment							1
Payments under agreement using exchange rate							0.8	1.1
Aggregate payments under agreement excluding potential milestones							1.8	2.3
Amount agreed to pay by the company on achievement of milestones	1.0			1.3
Maximum reimbursement agreed by the company							€ 1.8		$ 2.4