Fair Value - Fair value of warrant liability (Details) - Level 3 - Valuation Technique, Option Pricing Model	Aug. 31, 2020
Expected volatility | Warrant Liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted average significant input for fair value measurement	0.3856
Expected volatility | Contingent Value Rights Liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted average significant input for fair value measurement	0.5353
Risk free interest rates | Warrant Liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted average significant input for fair value measurement	0.0018
Risk free interest rates | Contingent Value Rights Liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted average significant input for fair value measurement	0.0014
Expected term (in years) | Warrant Liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted average significant input for fair value measurement	0.03
Expected term (in years) | Contingent Value Rights Liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted average significant input for fair value measurement	0.01
Annual dividend yield | Warrant Liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted average significant input for fair value measurement	0.0129
Annual dividend yield | Contingent Value Rights Liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted average significant input for fair value measurement	0.020