v3.21.2

Convertible notes (Schedule of Convertible Notes) (Details)				12 Months Ended
	Apr. 30, 2020 USD ($) shares	Apr. 25, 2019 shares	Apr. 18, 2018 USD ($) $ / shares	Dec. 31, 2020 USD ($) $ / shares	Jan. 31, 2020
Short-term Debt [Line Items]
Interest rate			2.50%		8.00%
Proceeds from Notes Payable			$ 5,779,602,000
Debt Instrument, Term			5 years
Debt Instrument, Convertible, Conversion Price | $ / shares			$ 1.50
Debt Instrument, Convertible, Number of Equity Instruments			3,853,068
2018 Notes
Short-term Debt [Line Items]
Debt Instrument, Convertible, Conversion Price | $ / shares				$ 1.38
Debt Instrument Dividend Liability				$ 500,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt				$ 5,300,000
Debt Instrument Issue Date price | $ / shares				$ 1.07
Century Skyway Limited
Short-term Debt [Line Items]
Number of shares to sell | shares		5,100
Century Skyway Limited | 2019 Notes
Short-term Debt [Line Items]
Principal amount	$ 160,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt	3,600,000
Principal amount to be surrendered in the disposal	$ 3,760,000
Number of shares to sell | shares	5,100

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