Capital Stock (Authorized, Issued and Reserved shares of common stock) (Detail)	6 Months Ended
	Jun. 30, 2016 $ / shares shares
Reserved for issuance	140,565,812
Total common shares issued and outstanding at June 30, 2016	173,029,840
Total common shares outstanding and reserved for issuance at June 30, 2016	313,595,652
Warrants with common stock additional purchase rights associated with December 2014 private placement [Member]
Reserved for issuance	50,189,431
Strike Price | $ / shares	$ 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 | $ / shares	$ 0.2500
Expiry	Sep. 08, 2024
Shares reserved under outstanding stock options and options available for grant [Member]
Reserved for issuance	52,107,279
Shares reserved for future issuance under the Employee Stock Purchase Plan [Member]
Reserved for issuance	157,454
Warrants to purchase common stock associated with December 2014 venture loan and security agreement [Member]
Reserved for issuance	2,492,523
Strike Price | $ / shares	$ 0.1003
Expiry	Dec. 23, 2024
Outstanding warrants issued in June 2012 [Member]
Reserved for issuance	437,158
Strike Price | $ / shares	$ 0.2745
Expiry	Jun. 29, 2017
Outstanding warrants issued in May 2013, vesting May 2013 [Member]
Reserved for issuance	20,655,737
Strike Price | $ / shares	$ 0.2745
Expiry	May 17, 2020
Outstanding warrants issued in May 2013, vesting August 2013 [Member]
Reserved for issuance	14,426,230
Strike Price | $ / shares	$ 0.2745
Expiry	Aug. 09, 2020