ARCALYST (rilonacept) Product Revenue (Details) (USD $)	3 Months Ended			6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Mar. 31, 2010	Jun. 30, 2011	Jun. 30, 2010
Product Revenue [Abstract]
Previously deferred ARCALYST net product sales recognized as revenue			$ 4,800,000		$ 4,800,000
Change in accounting estimate, deferred revenue - lower net loss per share (in dollars per share)					$ 0.06
ARCALYST net product sales	5,039,000	5,197,000		9,466,000	15,049,000
ARCALYST net product sales, excluding deferred sales recognized as revenue					10,200,000
Cost of goods sold related to ARCALYST sales	$ 395,000	$ 405,000		$ 777,000	$ 1,122,000