Business Segments - Business segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting Information [Line Items]
Revenues	$ 10,477	$ 10,696	$ 20,610	$ 20,810
Operating profit (loss)	5,372	5,176	10,296	9,823
General and administrative expenses	(2,552)	(2,409)	(4,594)	(4,202)
Total operating profit	2,820	2,767	5,702	5,621
Interest expense	829	1,129	1,740	2,135
Depreciation, depletion and amortization			5,210	5,724
Capital expenditures	6,313	979	12,518	2,185
Operating Segments
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization	2,543	2,819	5,078	5,599
Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment
Segment Reporting Information [Line Items]
General and administrative expenses	(551)	0	(551)	0
Industrial and commercial | Operating Segments
Segment Reporting Information [Line Items]
Revenues	1,445	1,420	2,898	2,490
Operating profit (loss)	830	822	1,642	1,413
General and administrative expenses	(340)	(412)	(590)	(708)
Depreciation, depletion and amortization	360	359	723	637
Capital expenditures	248	65	393	545
Mining royalty lands | Operating Segments
Segment Reporting Information [Line Items]
Revenues	3,231	3,264	6,194	6,546
Operating profit (loss)	2,985	3,023	5,709	6,036
General and administrative expenses	(342)	(291)	(620)	(514)
Depreciation, depletion and amortization	159	151	308	334
Capital expenditures	22	0	42	0
Development | Operating Segments
Segment Reporting Information [Line Items]
Revenues	305	467	608	953
Operating profit (loss)	137	174	77	224
General and administrative expenses	(1,029)	(1,461)	(2,307)	(2,546)
Depreciation, depletion and amortization	43	41	85	96
Capital expenditures	5,927	867	11,881	1,461
Multifamily | Operating Segments
Segment Reporting Information [Line Items]
Revenues	5,496	5,545	10,910	10,821
Operating profit (loss)	1,420	1,157	2,868	2,150
General and administrative expenses	(290)	(245)	(526)	(434)
Depreciation, depletion and amortization	1,981	2,268	3,962	4,532
Capital expenditures	$ 116	$ 47	$ 202	$ 179