Capital Stock (Authorized, Issued and Reserved shares of common stock) (Detail) - Class Of Stock [Domain] - $ / shares	6 Months Ended
	Jun. 30, 2015	May. 17, 2013
Reserved for issuance	111,012,745
Strike Price		$ 0.2745
Total common shares issued and outstanding at June 30, 2015	172,786,907
Total common shares outstanding and reserved for issuance at June 30, 2015	283,799,652
Warrants with common stock additional purchase rights associated with December 2014 private placement [Member]
Reserved for issuance	50,189,431
Strike Price	$ 0.1003
Expiry	Dec. 23, 2021
Warrants to purchase common stock associated with September 2014 consulting agreement with Danforth Advisors [Member]
Reserved for issuance	100,000
Strike Price	$ 0.2500
Expiry	Sep. 08, 2024
Shares reserved under outstanding stock options and options available for grant [Member]
Reserved for issuance	22,311,279
Rights Associated With Employee Stock Purchase Plan [Member]
Reserved for issuance	400,387
Warrants to purchase common stock associated with December 2014 venture loan and security agreement [Member]
Reserved for issuance	2,492,523
Strike Price	$ 0.1003
Expiry	Dec. 23, 2024
Warrant Two [Member]
Reserved for issuance	437,158
Strike Price	$ 0.2745
Expiry	Jun. 29, 2017
Warrant Three [Member]
Reserved for issuance	20,655,737
Strike Price	$ 0.2745
Expiry	May 17, 2020
Warrant Four [Member]
Reserved for issuance	14,426,230
Strike Price	$ 0.2745
Expiry	Aug. 09, 2020