Debt - 7.5% Notes (Details) $ / shares in Units, $ in Thousands				1 Months Ended	12 Months Ended
	Dec. 04, 2018 USD ($)	Jun. 29, 2018 USD ($)	Feb. 09, 2017 USD ($)	Jun. 30, 2013 USD ($) D $ / shares shares	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Nov. 17, 2017 USD ($)	Feb. 21, 2017 USD ($)	Aug. 27, 2013 USD ($)
Long-term debt
Aggregate principal amount						$ 89,094	$ 79,928
7.5% Notes
Long-term debt
Interest rate (as a percent)				7.50%		7.50%	7.50%
Debt issuance amount				$ 150,000
Conversion price of shares (in dollars per share) | $ / shares				$ 15.80
Percentage of the trade price of common stock that the conversion price must be at premium for the Company to force conversion				40.00%
Number of days within 30 consecutive trading days in which the trade price of the entity's common stock must be at premium of the conversion price for the Company to force conversion | D				20
Number of consecutive trading days used to determine the conversion obligation on the notes for the Company to force conversion | D				30
Period during which the debt instrument principal balance is required to be paid following its issuance				7 years
Repayment in shares at maturity covenant, maximum number of shares (in shares) | shares				13,993,630
Repurchased face amount during period	$ 50,000	$ 25,000
Repayments of debt		$ 500
Repayments of convertible debt	$ 50,500
Aggregate principal amount						$ 50,000	$ 50,000
7.5% Notes | Green Energy Investment Holdings, LLC
Long-term debt
Principal amount transferred									$ 11,800	$ 5,000
Aggregate principal amount						32,900
7.5% Notes | Mr. Pickens
Long-term debt
Principal amount transferred								$ 40,000
Repurchased face amount during period			$ 25,000
Repayments of convertible debt			$ 21,800
Gain (loss) on repurchase of debt instrument					$ 3,200
7.5% Notes | Other Third Parties
Long-term debt
Aggregate principal amount						$ 17,100