Restatement of Previously Issued Consolidated Financial Statements - Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 2,724	$ 2,543
Account receivable	5,419	7,889
Prepaid expenses	766	1,182
Total current assets	8,909	11,614
Royalty interests in oil and natural gas properties, net of accumulated amortization of $144,445 and $130,342 respectively	207,505	219,192
Property and equipment, net of accumulated depreciation of $179 and $75	427	517
Deferred tax asset, net	55,773	56,352
Other assets	3,015	2,530
Total assets	275,629	290,205
Current liabilities:
Accounts payable and accrued expenses	1,540	2,206
Other current liabilities	1,557
Total current liabilities	3,097	2,206
Credit facility	39,800	42,500
Warrant liability	3,503	8,631
Other liabilities	828	473
Total liabilities	47,228	53,810
Commitments and contingencies (See Note 15)
Shareholders' equity:
Preferred stock, $0.0001 par value; 1,000,000 shares authorized; none issued and outstanding
Additional paid in capital	121,053	117,561
Non-controlling interests	88,637	96,089
Retained earnings	18,702	22,736
Total shareholders' equity	228,401	236,395	$ 255,014	$ 289,157
Total liabilities, shareholders' equity	275,629	290,205
As Previously Reported [Member]
Current assets:
Cash and cash equivalents	2,724	2,543
Account receivable	5,419	7,889
Prepaid expenses	766	1,182
Total current assets	8,909	11,614
Royalty interests in oil and natural gas properties, net of accumulated amortization of $144,445 and $130,342 respectively	207,505	219,192
Property and equipment, net of accumulated depreciation of $179 and $75	427	517
Deferred tax asset, net	55,773	56,352
Other assets	3,015	2,530
Total assets	275,629	290,205
Current liabilities:
Accounts payable and accrued expenses	1,540	2,206
Other current liabilities	1,557
Total current liabilities	3,097	2,206
Credit facility	39,800	42,500
Other liabilities	828	473
Total liabilities	43,725	45,179
Commitments and contingencies (See Note 15)
Shareholders' equity:
Preferred stock, $0.0001 par value; 1,000,000 shares authorized; none issued and outstanding
Additional paid in capital	123,457	129,127
Non-controlling interests	108,438	115,890
Total shareholders' equity	231,904	245,026	269,714	$ 289,157
Total liabilities, shareholders' equity	275,629	290,205
Adjustments [Member]
Current liabilities:
Warrant liability	3,503	8,631
Total liabilities	3,503	8,631
Commitments and contingencies (See Note 15)
Shareholders' equity:
Preferred stock, $0.0001 par value; 1,000,000 shares authorized; none issued and outstanding
Additional paid in capital	(2,404)	(11,566)
Non-controlling interests	(19,801)	(19,801)
Retained earnings	18,702	22,736
Total shareholders' equity	(3,503)	(8,631)	(14,700)
Class C common stock [Member]
Shareholders' equity:
Common stock, value	4	4
Total shareholders' equity	4	4	4
Class C common stock [Member] | As Previously Reported [Member]
Shareholders' equity:
Common stock, value	4	4
Total shareholders' equity	4	4	4
Class A common stock [Member]
Shareholders' equity:
Common stock, value	5	5
Total shareholders' equity	5	5	5
Class A common stock [Member] | As Previously Reported [Member]
Shareholders' equity:
Common stock, value	5	5
Total shareholders' equity	$ 5	$ 5	$ 5