Investment in Laramie Energy, LLC - Summarized Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
ASSETS
Current assets	$ 719,765				$ 719,765		$ 1,032,174
Current liabilities	806,570				806,570		1,034,322
REVENUE
Income from operations	(25,443)		$ 48,621		(206,616)	$ 70,044
Net income (loss)	(40,560)	$ (222,337)	28,169	$ 61,092	(262,897)	89,261
Laramie Energy Company
ASSETS
Current assets	16,964				16,964		23,367
Non-current assets	375,679				375,679		393,575
Current liabilities	20,706				20,706		229,687
Non-current liabilities	283,728				283,728		$ 85,287
REVENUE
Natural gas and oil revenues	23,545		43,270		58,258	111,194
Income from operations	(8,699)		(8,205)		(7,330)	5,538
Net income (loss)	$ (14,349)		$ (2,570)		$ (13,775)	$ (5,553)