Issue of options under equity incentive plan - Narrative (Detail) (2010 Equity Incentive Plan [Member], USD $)	1 Months Ended	3 Months Ended		1 Months Ended	3 Months Ended
	Dec. 31, 2010 Options Granted December 13, 2010 [Member]	Jan. 31, 2014 Options Granted December 13, 2010 [Member]	Oct. 31, 2013 Options Granted December 13, 2010 [Member]	May 31, 2011 Options Granted May 2011 [Member]	Jan. 31, 2014 Options Granted May 2011 [Member]	Oct. 31, 2013 Options Granted May 2011 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted	2,500,000			750,000
Employee stock option vesting rights		1/3 on December 13, 2010, 1/3 vested on November 17, 2011 and the balance vested on November 17, 2012.			The options vested 1/3 upon grant date, 1/3 vested on February 1, 2012 and the balance vested on February 1, 2013.
Stock options expiration date		Nov. 17, 2020			Feb. 01, 2018
Number of options, outstanding		2,500,000	2,500,000		750,000	750,000
Weighted average grant date fair value per option granted		$ 0.81			$ 0.95
Weighted average remaining contractual life		6 years			4 years
Options exercisable			2,500,000		750,000