Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Oil and gas properties:
Accumulated depreciation, depletion, amortization and impairment	$ (98,826)	$ (95,281)
Net oil and gas properties	250,706	253,871
Pipeline facilities and equipment	12,714	12,714
Base gas	2,122	2,122
Furniture and fixtures, computer hardware and software, and other equipment	6,688	6,649
Accumulated depreciation and amortization	(4,356)	(3,922)
Net other property and equipment	17,168	17,563
Total net property and equipment	267,874	271,434
Proved Oil and Gas Properties [Member]
Oil and gas properties:
Oil and gas properties, gross	344,147	343,736
Unproved Properties Not Subject To Depletion [Member]
Oil and gas properties:
Oil and gas properties, gross	$ 5,385	$ 5,416