CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net income	$ 4,882,000	$ 4,047,000	$ 40,094,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	10,975,000	11,462,000	12,946,000
Deferred income taxes	1,496,000	1,813,000	7,941,000
Gain on remeasurement of invest in real estate partnership	0	0	(51,139,000)
Equity in loss of joint ventures	11,937,000	5,721,000	5,754,000
Gain on sale of equipment and property	(14,000)	(904,000)	(880,000)
Stock-based compensation	1,738,000	1,569,000	1,111,000
Net changes in operating assets and liabilities:
Accounts receivable	120,000	(373,000)	837,000
Deferred costs and other assets	(499,000)	(1,972,000)	(346,000)
Accounts payable and accrued liabilities	3,028,000	(276,000)	1,888,000
Income taxes payable and receivable	(355,000)	1,121,000	3,518,000
Other long-term liabilities	(337,000)	130,000	518,000
Net cash provided by operating activities	32,971,000	22,338,000	22,242,000
Cash flows from investing activities:
Investments in properties	(11,217,000)	(27,615,000)	(16,530,000)
Investments in joint ventures	(46,693,000)	(21,578,000)	(13,436,000)
Return of capital from investments in joint ventures	9,210,000	20,770,000	22,279,000
Proceeds from sales of investments available for sale	0	4,317,000	69,865,000
Cash at consolidation of real estate partnership	0	0	3,704,000
Cash held in escrow	(63,000)	(45,000)	(220,000)
Proceeds from sale of assets	16,000	955,000	939,000
Net cash (used in) provided by investing activities	(48,747,000)	(23,196,000)	66,601,000
Cash flows from financing activities:
Proceeds from long-term debt	0	0	92,070,000
Repayment of long-term debt	0	0	(90,000,000)
Debt issue costs	0	0	(704,000)
Contribution from partner	0	27,894,000	0
Distribution to noncontrolling interest	(3,190,000)	(11,472,000)	(2,602,000)
Repurchase of company stock	(2,000,000)	0	(264,000)
Exercise of employee stock options	1,024,000	412,000	269,000
Net cash (used in) provided by financing activities	(4,166,000)	16,834,000	(1,231,000)
Net (decrease) increase in cash and cash equivalents	(19,942,000)	15,976,000	87,612,000
Cash and cash equivalents at beginning of year	177,497,000	161,521,000	73,909,000
Cash and cash equivalents at end of the year	157,555,000	177,497,000	161,521,000
Supplemental disclosures of cash flow information:
Interest	4,165,000	2,893,000	2,150,000
Income taxes	$ 927,000	$ (1,761,000)	$ (1,226,000)