Convertible Preferred Stock Warrant Liability - Additional Information (Details) - USD ($)		1 Months Ended				3 Months Ended		6 Months Ended
	Jul. 22, 2015	Oct. 31, 2014	Dec. 31, 2012	Apr. 30, 2012	May. 31, 2009	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2015	Jul. 31, 2014	Jan. 31, 2015	Dec. 31, 2010	Jun. 30, 2009
Class Of Stock [Line Items]
Warrant to purchase convertible preferred stock					21,299					76,630	70,287	34,397
Exercise price per share of warrants	$ 4.70									$ 6.04	$ 4.70
Payment for warrant holders								$ 600,000
Public offering price	$ 13.00										$ 13.00
Aggregate liability	$ 400,000
Warrants terminated	10,099
Gain on termination of warrants	$ 100,000
December 2010 warrant
Class Of Stock [Line Items]
Remeasurement gain (loss) from change in fair value of warrants						$ 100,000	$ (17,000)	(100,000)	$ (100,000)
May and June 2009 warrants
Class Of Stock [Line Items]
Remeasurement gain (loss) from change in fair value of warrants						$ 100,000	(5,000)	$ (100,000)	(48,000)
Initial Public Offering
Class Of Stock [Line Items]
Warrant to purchase convertible preferred stock	21,529
Exercise price per share of warrants	$ 4.70
Public offering price	$ 13.00					$ 13.00		$ 13.00
Warrants terminated	10,099
Warrants issued					21,299
Series Alpha Convertible Preferred Stock
Class Of Stock [Line Items]
Warrant to purchase convertible preferred stock											70,287
Exercise price per share of warrants		$ 4.70	$ 4.70	$ 4.70							$ 4.70
Warrants issued to purchase convertible preferred stock		66,026	66,026	66,026
Aggregate liability	$ 700,000
Warrant conversion ratio	100.00%
Series Alpha Convertible Preferred Stock | Minimum
Class Of Stock [Line Items]
Warrant expiry period								2022-04
Series Alpha Convertible Preferred Stock | Maximum
Class Of Stock [Line Items]
Warrant expiry period								2022-12
Series Alpha Convertible Preferred Stock | April 2012, December 2012 and October 2014 warrants
Class Of Stock [Line Items]
Remeasurement gain (loss) from change in fair value of warrants						$ (100,000)	$ (9,000)	$ (300,000)	$ (100,000)
Series Alpha Convertible Preferred Stock | Initial Public Offering
Class Of Stock [Line Items]
Exercise price per share of warrants						$ 13.00		$ 13.00
Convertible Preferred Stock
Class Of Stock [Line Items]
Warrant to purchase convertible preferred stock	2,769				21,299							34,397
Common Stock
Class Of Stock [Line Items]
Warrant to purchase convertible preferred stock	87,828				21,299
Common Stock | May and June 2009 warrants
Class Of Stock [Line Items]
Warrant to purchase convertible preferred stock	2,769
Common Stock | Initial Public Offering
Class Of Stock [Line Items]
Warrant to purchase convertible preferred stock	13,752