Fair Value of Financial Instruments and Fair Value Measurements - Schedule of Fair Value Measurement (Details) - Contracts for differences - Level 3	Dec. 31, 2019 $ / MWh
Min. | Risk of non-performance
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount rate	0.0005
Min. | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount rate	0.0169
Min. | Forward pricing
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount rate	3.80
Max. | Risk of non-performance
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount rate	0.0045
Max. | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount rate	0.0183
Max. | Forward pricing
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount rate	7.03