ARCALYST (rilonacept) Product Revenue (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Mar. 31, 2010	Sep. 30, 2011	Sep. 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	5,468,000	4,936,000		14,934,000	19,985,000
ARCALYST net product sales, excluding deferred sales recognized as revenue					15,200,000
Cost of goods sold related to ARCALYST sales	$ 450,000	$ 372,000		$ 1,227,000	$ 1,494,000