Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Oil and gas sales									$ 40,081	$ 68,463	$ 98,655
Gain (loss) on commodity derivative instruments									(1,200)		(1,456)
Total revenue	$ 9,497	$ 9,669	$ 6,115	$ 13,600	$ 13,051	$ 15,908	$ 18,246	$ 21,258	38,881	68,463	97,199
Operating expenses:
Production and ad valorem taxes									2,807	4,262	5,143
Marketing and transportation									1,993	2,396	2,368
Amortization of royalty interests in oil and natural gas properties									14,103	12,737	16,962
General, administrative, and other									11,997	11,912	9,544
Total operating expenses									30,900	31,307	34,017
Operating income	1,469	2,014	(1,104)	5,602	4,968	8,081	10,776	13,331	7,981	37,156	63,182
Other income (expense):
Gain on the sale of assets											41,382
Change in fair value of warrant liability									5,128	6,069	27,800
Other income									125	165	46
Interest expense									(2,197)	(2,489)	(2,350)
Total other income (expense)									3,056	3,745	66,878
Income before income taxes									11,037	40,901	130,060
Provision for income taxes									589	3,918	3,292
Income from continuing operations									10,448	36,983	126,768
Income from discontinued operations											2,139
Net income									10,448	36,983	128,907
Net income attributable to non-controlling interests									(2,748)	(16,564)	(10,982)
Net income attributable to common shareholders/unitholders	$ (1,375)	$ 1,560	$ (368)	$ 7,883	$ 1,118	$ 16,400	$ 2,406	$ 495	$ 7,700	$ 20,419	$ 117,925
Earnings per common share:
Common shares - basic	$ (0.03)	$ 0.03	$ (0.01)	$ 0.17	$ 0.02	$ 0.36	$ 0.05	$ 0.01	$ 0.17	$ 0.44	$ 0.81
Common shares - diluted	$ (0.03)	$ 0.02	$ (0.01)	$ 0.11	$ 0.02	$ 0.22	$ 0.05	$ 0.01	$ 0.11	$ 0.39	$ 0.53
Weighted average number of shares outstanding:
Common shares - basic	46,099	46,055	46,001	45,967	45,956	45,899	45,858	45,856	46,031	45,893	45,855
Common shares - diluted	46,099	86,055	46,001	85,967	45,956	85,899	45,858	45,856	86,031	85,893	85,855