Fair Value - Additional Information (Details)		12 Months Ended
	Jun. 14, 2019 MW	Dec. 31, 2019 USD ($) $ / shares MW	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 10, 2016 USD ($)	Jan. 29, 2016 USD ($)	Dec. 15, 2015 USD ($) $ / shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash flow hedge gain to be reclassified within 12 months		$ 600,000
Interest rate percentage		6.00%
Embedded derivative liability		$ 6,200,000	$ 4,000,000	$ 4,200,000
Not designated as hedging instrument | Natural gas forward contract
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (loss) on derivative		(800,000)	2,200,000	(1,000,000)
Gain on the settlement of contracts		$ 3,600,000	3,400,000	$ 4,200,000
Convertible promissory notes | Convertible Promissory Notes due December 2020, Recourse
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt face amount					$ 260,000,000	$ 75,000,000	$ 25,000,000	$ 160,000,000
Interest rate percentage		6.00%
Convertible stock price (in dollars per share) | $ / shares		$ 20.61						$ 11.25
Embedded derivative liability						$ 178,000,000
Preferred stock warrants | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stock warrants:		$ 0	$ 0
PPA II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of replacement megawatts | MW	9.8
PPA IIIb
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of replacement megawatts | MW		5
New Energy Server Systems | PPA II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of replacement megawatts | MW	30
New Energy Server Systems | PPA IIIb
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of replacement megawatts | MW		5