Convertible Preferred Stock (Details) (USD $)	0 Months Ended	12 Months Ended	0 Months Ended	1 Months Ended	12 Months Ended	0 Months Ended
	Mar. 29, 2012	Dec. 31, 2012	Aug. 13, 2012	Jul. 31, 2011	Dec. 31, 2014	Aug. 13, 2012
Convertible preferred stock
Gross proceeds		$ 34,992,000
Reverse stock split conversion ratio	2.0230
Series A convertible preferred stock
Convertible preferred stock
Shares issued				6,200,000
Issue price (in dollars per share)				$ 1.00
Gross proceeds				6,200,000
Issuance cost				100,000
Preferred stock, conversion ratio					1
Preferred stock, conversion ratio following Reverse Stock Split		(2.023)	2.023
Series A convertible preferred stock | Issuance under private placement
Convertible preferred stock
Number of shares of common stock in which preferred stock is convertible						3,064,753
Series B convertible preferred stock
Convertible preferred stock
Shares issued	6,770,563
Issue price (in dollars per share)	5.50
Gross proceeds	37,200,000
Issuance cost	2,200,000
Preferred stock, conversion ratio following Reverse Stock Split		1
Series B convertible preferred stock | Issuance under private placement
Convertible preferred stock
Number of shares of common stock in which preferred stock is convertible						6,770,563
Preferred stock, conversion ratio following Reverse Stock Split						1