Subsequent Event (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		0 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Issuance of common stock Aspire Capital	Apr. 16, 2013 Subsequent event Issuance of common stock
Public Offering
Common stock sold (in shares)			146,886	2,875,000
Common stock offering price (in dollars per share)				$ 5.25
Shares issued upon exercise of over-allotment options by underwriters				375,000
Proceeds, net of transaction costs	$ 874	$ 2,061		$ 14,000