Leases (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011 sqft item	Dec. 31, 2010	Dec. 31, 2008 item
Operating Leases
Area of laboratory and office space leased (in square feet)		73,646
Initial term of the lease agreement		7 years
Initial lease term		2		2
Extended additional term of lease agreement		5 years		5 years
Annual future minimum lease payments
2013	$ 1,749,000
2014	1,540,000
2015	1,634,000
2016	1,735,000
2017 and beyond	3,844,000
Total	10,502,000
Rent expense	$ 2,600,000	$ 2,300,000	$ 2,300,000