Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Revenues	$ 9,628	$ 8,495	$ 18,335	$ 14,348
Operating profit before corporate expenses	3,373	891	5,572	3,112
Corporate expenses	(1,307)	(1,050)	(2,142)	(1,829)
Corporate expenses	2,066	(159)	3,430	1,283
Interest expense	739	446	1,477	1,371
Depreciation, depletion and amortization			5,890	5,951
Capital expenditures	13,775	3,458	17,411	6,845
Asset Management [Member]
Segment Reporting Information [Line Items]
Revenues	912	588	1,751	1,300
Operating profit before corporate expenses	419	128	711	359
Corporate expenses	(225)	(288)	(369)	(502)
Depreciation, depletion and amortization	230	134	464	271
Capital expenditures	145	139	595	218
Mining Properties [Member]
Segment Reporting Information [Line Items]
Revenues	2,883	2,634	5,308	4,949
Operating profit before corporate expenses	2,498	2,400	4,681	4,494
Corporate expenses	(148)	(108)	(242)	(189)
Depreciation, depletion and amortization	189	58	244	123
Capital expenditures	11,126	0	11,217	0
Development [Member]
Segment Reporting Information [Line Items]
Revenues	408	451	791	768
Operating profit before corporate expenses	(581)	(411)	(1,299)	(797)
Corporate expenses	(816)	(522)	(1,337)	(941)
Depreciation, depletion and amortization	47	53	92	106
Capital expenditures	2,426	2,907	5,379	6,206
Stabilized Joint Venture [Member]
Segment Reporting Information [Line Items]
Revenues	5,425	4,822	10,485	7,331
Operating profit before corporate expenses	1,037	(1,226)	1,479	(944)
Corporate expenses	(118)	(132)	(194)	(197)
Depreciation, depletion and amortization	2,402	4,143	4,966	5,331
Capital expenditures	78	412	220	421
Total Segments [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization	$ 2,868	$ 4,388	$ 5,766	$ 5,831