Property and Equipment, Net (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Property and equipment
Cost	$ 6,175		$ 6,175		$ 5,072
Accumulated depreciation	(3,342)		(3,342)		(3,077)
Total property and equipment, net of accumulated depreciation	2,833		2,833		1,995
Depreciation of property and equipment	362	342	919	849
Reduction to cost and accumulated depreciation of fully depreciated equipment and leasehold improvements no longer in use			654	229
Computer hardware
Property and equipment
Cost	3,343		3,343		2,885
Leasehold improvements
Property and equipment
Cost	1,219		1,219		849
Furniture and fixtures
Property and equipment
Cost	1,077		1,077		765
Computer software
Property and equipment
Cost	475		475		545
Office equipment
Property and equipment
Cost	$ 61		$ 61		$ 28