Private Securities Offerings - Additional Information (Detail) - USD ($)								1 Months Ended	12 Months Ended
	Mar. 04, 2020	Feb. 28, 2020	Dec. 30, 2019	Dec. 20, 2019	May 08, 2019	Mar. 23, 2018	Nov. 30, 2017	Jan. 31, 2020	May 31, 2020	May 31, 2019	May 31, 2018	Jun. 30, 2020	Feb. 04, 2020	Nov. 30, 2019	Apr. 05, 2019	Feb. 13, 2019	Jun. 15, 2018	Nov. 24, 2017	Oct. 11, 2017	Sep. 08, 2017	May 31, 2017
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share														$ 0.45
Common stock, par value									$ 0.001	$ 0.001
Warrants to purchase common shares, shares													833,332
Term of warrants															5 years
Common stock issued									$ 154,552		$ 104,546
Proceeds From Exercise Of Warrants									38,421,468		$ 3,161,131
Maximum [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Purchase price, per share												$ 1.35
Minimum [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Purchase price, per share												$ 0.35
Private Warrant Exchange [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Common stock, par value	$ 0.001	$ 0.001	$ 0.001	$ 0.001	$ 0.001			$ 0.001
Warrants to purchase common shares, shares					7,541,279
Proceeds from issuance of common shares					$ 3,000,000
Stock issued during period shares warrant exercise	88,000	8,626,745	2,676,000	4,690,000				4,448,000
Proceeds From Exercise Of Warrants	$ 36,000,000,000	$ 2,200,000	$ 1,100,000	$ 800,000				$ 1,900,000
Professional Fees					$ 300,000
Share Price			$ 0.50		$ 0.40			$ 0.50
Stock Issued During Period, Shares, Warrant Exercised					11,311,917
Noncash inducement interest expense					$ 200,000				$ 5,500,000
Private Warrant Exchange [Member] | Maximum [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share		$ 0.75	0.50	$ 0.75				0.50
Share Price	$ 0.75	0.45		0.25
Private Warrant Exchange [Member] | Minimum [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share		0.30	$ 0.50	0.45				$ 0.50
Share Price	$ 0.45	$ 0.18		$ 0.22
Private Warrant Exchange [Member] | Additional Shares [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Warrants to purchase common shares, shares					3,770,638
Stock issued during period shares warrant exercise	8,000	784,245	446,000	1,340,000				408,000
Private Warrant Exchange [Member] | Actual Shares [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Stock issued during period shares warrant exercise	80,000	7,842,500	2,230,000	3,350,000				4,040,000
Common Stock [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Common stock sold at private equity offering									379,880		310,526
Common stock issued									$ 380		$ 311
Stock issued during period shares warrant exercise											0
Offer To Amend And Exercise [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share																		$ 0.50
Make Whole Securities [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Common stock sold at private equity offering							503,015
Warrants to purchase common shares, shares							251,504
Make Whole Securities [Member] | Waiver And Subscription Agreement [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share																			$ 0.75	$ 1.00
Purchase price, per share																			$ 0.65	0.75
Placement Agent
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share															$ 0.50	$ 0.50	$ 0.55
Warrants to purchase common shares, shares														655,305	938,790	965,563	133,600
Term of warrants											5 years			5 years		5 years	5 years
Placement Agent | Maximum [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share														$ 0.444
Placement Agent | Minimum [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share														$ 0.40
Placement Agent | Make Whole Securities [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share							$ 0.715
Warrants to purchase common shares, shares									26,702
Placement Agent | Make Whole Securities [Member] | Waiver And Subscription Agreement [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share																				$ 0.825
Private Equity Offering
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share										$ 0.75	$ 0.75										$ 1.00
Warrant covering common stock shares purchased, percentage										50.00%	100.00%
Common stock sold at private equity offering										46,975,170	35,286,904
Common stock, par value										$ 0.001
Proceeds from private equity offering											$ 17,600,000
Warrants to purchase common shares, shares											35,286,904
Proceeds from issuance of common shares										$ 23,500,000
Term of warrants										5 years	5 years
Purchase price, per share											$ 0.50
Private Equity Offering | Placement Agent
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share										$ 0.50	$ 0.55
Warrants to purchase common shares, shares										4,446,917	2,813,491
Term of warrants										5 years
Professional Fees										$ 2,700,000
Private Equity Offering | Warrant Holders [Member] | Offer To Amend And Exercise [Member] | Common Stock [Member]
Equity and Equity Units Offering Disclosure [Line Items]
Common stock issued						$ 2,470,585
Private Equity Offering | Warrants
Equity and Equity Units Offering Disclosure [Line Items]
Exercise price of warrants, per share											$ 0.75
Warrants to purchase common shares, shares										23,487,585