Assumptions used in Estimating Fair Value of Convertible Note Redemption Provision Derivative Liability (Detail)	1 Months Ended		12 Months Ended
	Jan. 30, 2019 yr $ / shares	Nov. 15, 2018 yr $ / shares	May 31, 2019 yr $ / shares
Fair value of underlying stock
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, price per share | $ / shares	$ 0.49	$ 0.57
Fair value of underlying stock | June Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, price per share | $ / shares			$ 0.39
Fair value of underlying stock | January Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, price per share | $ / shares			$ 0.39
Risk free rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Liability, Measurement Input	2.52	2.78
Risk free rate | June Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Liability, Measurement Input			2.21
Risk free rate | January Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Liability, Measurement Input			1.95
Expected Term (In Years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, expected term	2 years	1 year 7 months 9 days
Expected Term (In Years) | June Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, expected term			1 year 25 days
Expected Term (In Years) | January Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, expected term			1 year 8 months 1 day
Stock price volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Liability, Measurement Input	61	58.8
Stock price volatility | June Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Liability, Measurement Input			62.2
Stock price volatility | January Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Liability, Measurement Input			62.2
Expected dividend yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, dividend yield	0.00%	0.00%
Expected dividend yield | June Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, dividend yield			0.00%
Expected dividend yield | January Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, dividend yield			0.00%
Discount factor
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Liability, Measurement Input	85	85
Discount factor | June Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Liability, Measurement Input			85
Discount factor | January Note
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Liability, Measurement Input			85