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Collaborations And Other Agreements (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended	3 Months Ended	9 Months Ended		3 Months Ended			9 Months Ended		12 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 GlaxoSmithKline [Member]	Sep. 30, 2010 GlaxoSmithKline [Member]	Sep. 30, 2011 GlaxoSmithKline [Member]	Sep. 30, 2010 GlaxoSmithKline [Member]	Dec. 31, 2006 GlaxoSmithKline [Member]	Sep. 30, 2011 Novartis International Pharmaceutical Ltd. [Member]	Sep. 30, 2010 Novartis International Pharmaceutical Ltd. [Member]	Sep. 30, 2011 Novartis International Pharmaceutical Ltd. [Member]	Sep. 30, 2010 Novartis International Pharmaceutical Ltd. [Member]	Dec. 31, 2009 Novartis International Pharmaceutical Ltd. [Member]	Sep. 30, 2011 Morphotek Agreement [Member]	Sep. 30, 2011 Morphotek Agreement [Member]	Sep. 30, 2010 Morphotek Agreement [Member]	Sep. 30, 2011 US Government [Member]	Sep. 30, 2010 US Government [Member]	Dec. 31, 2009 US Government [Member]	Sep. 30, 2011 US Government [Member]	Sep. 30, 2010 US Government [Member]	Dec. 31, 2009 US Government [Member]	Sep. 30, 2011 Aegera Therapeutics, Inc. [Member]	Sep. 30, 2010 Aegera Therapeutics, Inc. [Member]	Sep. 30, 2011 Aegera Therapeutics, Inc. [Member]	Sep. 30, 2010 Aegera Therapeutics, Inc. [Member]	Sep. 30, 2011 Five Prime Therapeutics Agreement [Member]	Sep. 30, 2011 Five Prime Therapeutics Agreement [Member]
Non-refundable payment received									$ 24,000					$ 207,500
Costs reimbursed or reimbursable for research and development expenses					2,420	17,802	14,270	48,838		233		1,035	1,158		1,033	3,419	0
Number of doses of raxibacumab agreed to purchase																							45,000
Delivery period of raxibacumab in years																							3
Expected proceeds as deliveries are completed																				142,000
Product revenue recognized	30,833	7,295	65,587	33,963														12,048	7,295		38,944	33,963
Manufacturing and development services revenue recognized	2,747	5,677	19,011	15,177														799	600		2,169	1,438
Entitled to receive approximately contract upon FDA licensure of raxibacumab																					20,000
Paid license and equity investment aggregate value																										20,000
Collaboration expense	38,758	42,471	156,645	151,331							2,510													593	579	1,816	1,748	628	1,407
Other-than-temporary impairment																										240
Wrote down investment																								3,150		3,150
Proceeds from divestitures																										320
Gain on sale of investment																										80
Research costs incurred and expensed																													50,000
Development and commercial milestone payments																													445,000
Revenue recognized	$ 442	$ 37,810	$ 854	$ 86,948							$ 36,133		$ 82,806