Property and Equipment (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			80 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Property and equipment
Property and equipment, gross	$ 3,106	$ 2,910		$ 3,106
Less accumulated depreciation and amortization	(2,296)	(1,749)		(2,296)
Property and equipment, net	810	1,161		810
Depreciation expense	571	590	672	2,508
Gains (losses) on the disposal of long-lived assets	18		117	135
Furniture and fixtures
Property and equipment
Property and equipment, gross	247	242		247
Computer and office equipment
Property and equipment
Property and equipment, gross	123	129		123
Software
Property and equipment
Property and equipment, gross	103	103		103
Leasehold improvements - building
Property and equipment
Property and equipment, gross	60			60
Scientific equipment
Property and equipment
Property and equipment, gross	$ 2,573	$ 2,436		$ 2,573