Significant Accounting Policies (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Summary of revenues
Royalty revenue	$ 110		$ 2,034
Collaborative and other research and development revenues:
Collaborative and other research and development	711	4,210	2,341	16,431
Total revenues	821	4,210	4,375	16,431
U.S. Department of Health and Human Services [Member]
Collaborative and other research and development revenues:
Collaborative and other research and development	415	3,914	1,749	8,073
Shionogi (Japan) [Member]
Collaborative and other research and development revenues:
Collaborative and other research and development	296	296	592	592
Mundipharma (United Kingdom) [Member]
Collaborative and other research and development revenues:
Collaborative and other research and development				$ 7,766