Property and Equipment, Net (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Property and equipment
Cost	$ 6,476		$ 6,476		$ 5,072
Accumulated depreciation	(3,634)		(3,634)		(3,077)
Property and equipment, net	2,842		2,842		1,995
Depreciation of property and equipment	275	261	557	507
Write-offs of fixed assets	0	0	0	0
Reduction to cost and accumulated depreciation of fully depreciated equipment and leasehold improvements no longer in use				229
Furniture and fixtures
Property and equipment
Cost	1,075		1,075		765
Computer hardware
Property and equipment
Cost	3,610		3,610		2,885
Office equipment
Property and equipment
Cost	36		36		28
Computer software
Property and equipment
Cost	585		585		545
Leasehold improvements
Property and equipment
Cost	$ 1,170		$ 1,170		$ 849