Selected Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2011

Selected Quarterly Financial Data [Abstract]

Selected Quarterly Financial Data

	Quarters Ended
	March 31,			June 30,			September 30,			December 31,
2011:
Collaboration revenue	$	14,709		$	15,799		$	14,940		$	14,941
Operating expenses	$	(23,774	)	$	(26,175	)	$	(26,430	)	$	(26,940	)
Loss from operations	$	(9,065	)	$	(10,376	)	$	(11,490	)	$	(11,999	)
Net loss	$	(8,452	)	$	(9,474	)	$	(10,044	)	$	(10,871	)
Basic and diluted net loss per common share	$	(0.24	)	$	(0.27	)	$	(0.29	)	$	(0.31	)
Weighted-average common shares used in the calculation of basic and diluted net loss per common share		34,663			34,888			34,909			35,375
2010:
Collaboration revenue	$	15,734		$	15,792		$	14,350		$	16,632
Operating expenses	$	(33,421	)	$	(23,229	)	$	(21,087	)	$	(17,496	)
Loss from operations	$	(17,687	)	$	(7,437	)	$	(6,737	)	$	(864	)
Net loss	$	(17,465	)	$	(7,240	)	$	(5,443	)	$	(3,889	)
Basic and diluted net loss per common share	$	(0.51	)	$	(0.21	)	$	(0.16	)	$	(0.11	)
Weighted-average common shares used in the calculation of basic and diluted net loss per common share		33,953			34,053			34,570			34,573