Selected Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues:
Product	$ 5,263		$ 1,076		$ 4,948		$ 9,136		$ 6,834		$ 7,140		$ 6,783		$ 15,167		$ 20,423	$ 35,924	$ 49,021
Collaborative research and development	1,931		2,028		1,609		1,300		1,078		18,569		15,868		14,362		6,868	49,977	70,918
Revenue sharing arrangement	2,331		839		417		1,044		0		0		0		250		4,631	150	450
Government awards	0		0		0		0		0		632		258		1,357		0	2,247	3,476
Total revenues	9,525		3,943		6,974		11,480		7,912		26,341		22,909		31,136		31,922	88,298	123,865
Costs and operating expenses:
Cost of product revenues	4,764		494		3,631		5,665		5,779		6,397		5,829		12,642		14,554	30,647	41,781
Research and development	8,829		6,831		8,624		7,322		10,594		14,191		15,650		16,349		31,606	56,785	61,049
Selling, general and administrative	5,783		5,832		7,169		8,124		7,286		7,909		6,789		9,395		26,908	31,379	36,942
Total costs and operating expenses	19,376		13,157		19,424		21,111		23,659		28,497		28,268		38,386		73,068	118,811	139,772
Loss before income taxes	(9,858)		(9,227)		(12,617)		(9,688)		(15,711)		(2,140)		(5,442)		(7,293)		(41,390)	(30,587)	(16,309)
Net loss	$ (9,813)		$ (9,262)		$ (12,605)		$ (9,623)		$ (15,538)		$ (2,309)		$ (5,519)		$ (7,490)		$ (41,303)	$ (30,857)	$ (16,550)
Net loss per share of common stock, basic and diluted (dollars per share)	$ (0.26)		$ (0.24)		$ (0.33)		$ (0.25)		$ (0.41)		$ (0.06)		$ (0.15)		$ (0.21)		$ (1.08)	$ (0.84)	$ (0.46)
Weighted average common shares used in computing net loss per share of common stock, basic and diluted (shares)	38,329	[1]	38,102	[1]	38,060	[1]	37,842	[1]	37,581	[1]	37,118	[1]	36,296	[1]	36,057	[1]	38,231	36,768	35,674

[1] The full year net loss per share of common stock, basic and diluted, may not equal the sum of the quarters due to weighting of outstanding shares.