Investment in Laramie Energy, LLC - Summarized Financial Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
ASSETS
Current assets	$ 1,032,174				$ 586,592				$ 1,032,174	$ 586,592
Current liabilities	1,034,322				507,201				1,034,322	507,201
Income (loss) from operations	59,531	$ 18,405	$ 48,621	$ 21,423	20,408	$ 4,894	$ 28,983	$ 27,656	147,980	81,941	$ 93,961
Net income (loss)	35,439	$ (83,891)	$ 28,169	$ 61,092	13,886	$ (5,822)	$ 16,178	$ 15,185	40,809	39,427	72,621
Laramie Energy Company
ASSETS
Current assets	23,367				28,569				23,367	28,569
Non-current assets	393,575				788,515				393,575	788,515
Current liabilities	229,687				41,681				229,687	41,681
Non-current liabilities	$ 85,287				$ 293,084				85,287	293,084
Natural gas and oil revenues									193,906	226,974	157,879
Income (loss) from operations									(360,967)	34,206	6,019
Net income (loss)									$ (380,473)	$ 6,347	$ 30,837