Series B Convertible Preferred Stock (Details) (USD $)	1 Months Ended	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2013	Dec. 31, 2012
Series B Convertible Preferred Stock
Carrying value of convertible preferred stock		$ 42,876,000	$ 41,613,000
Series B Preferred Stock
Series B Convertible Preferred Stock
Period of closing of offering after which shares are convertible		5 years
Conversion price per share (in dollars per share)		$ 3.25
Percentage of cumulative dividend rate		11.50%
Period for accrual of dividend		5 years
Series B-1 Preferred Stock
Series B Convertible Preferred Stock
Number of shares sold	12,308
Offering price per share (in dollars per share)	$ 3,250
Carrying value of convertible preferred stock		5,186,000	3,923,000
Preferred stock, shares outstanding		0	0
Redemption value		31,102,000
Accretion of carrying value to redemption value		$ 1,263,000
Period to determine redemption value		5 years