Derivative Liabilities - Summary of Weighted-average Assumptions Used on Derivative Liabilities (Details)	6 Months Ended
	Oct. 31, 2018	Oct. 31, 2017
Minimum [Member]
Expected term (in years)	1 year	3 months 22 days
Minimum [Member] | Expected Average Volatility [Member]
Derivative liability, measurement input	107.00%	126.00%
Minimum [Member] | Expected Dividend Yield [Member]
Derivative liability, measurement input
Minimum [Member] | Risk-free Interest Rate [Member]
Derivative liability, measurement input	1.65%	0.99%
Maximum [Member]
Expected term (in years)	5 years	1 year
Maximum [Member] | Expected Average Volatility [Member]
Derivative liability, measurement input	237.00%	330.00%
Maximum [Member] | Expected Dividend Yield [Member]
Derivative liability, measurement input
Maximum [Member] | Risk-free Interest Rate [Member]
Derivative liability, measurement input	2.96%	1.34%