Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net earnings	$ 90,043,000	$ 62,860,000	$ 69,388,000
Adjustments to reconcile net earnings to net cash flow provided by operating activities:
Depreciation and amortization expense	39,902,000	35,518,000	30,191,000
Impairment charges	3,545,000	4,404,000	4,258,000
Gains on dispositions of real estate	(16,423,000)	(16,718,000)	(4,548,000)
Loss on extinguishment of debt			1,233,000
Deferred rent receivable	(3,458,000)	(2,778,000)	(2,903,000)
Allowance for credit loss on notes and mortgages receivable and direct financing leases	50,000	(132,000)	368,000
Amortization of above-market and below-market leases	14,000	(71,000)	(314,000)
Amortization of investment in direct financing leases	5,392,000	4,846,000	4,210,000
Amortization of debt issuance costs	946,000	1,013,000	1,053,000
Accretion expense	1,259,000	1,705,000	1,841,000
Stock-based compensation expense	4,775,000	3,997,000	3,130,000
Changes in assets and liabilities:
Accounts receivable	(784,000)	60,000	(1,048,000)
Prepaid expenses and other assets	(1,965,000)	(997,000)	(1,253,000)
Environmental remediation obligations	(28,088,000)	(6,335,000)	(9,490,000)
Accounts payable and accrued liabilities	(2,122,000)	(554,000)	(13,289,000)
Net cash flow provided by operating activities	93,086,000	86,818,000	82,827,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Property acquisitions	(137,275,000)	(194,292,000)	(149,955,000)
Capital expenditures		(271,000)	(282,000)
Addition to construction in progress	(56,000)	(312,000)	(275,000)
Proceeds from dispositions of real estate	24,204,000	24,796,000	5,433,000
Deposits for property acquisitions	(8,265,000)	3,298,000	(2,368,000)
Issuance of notes and mortgages receivable	(19,312,000)	(13,515,000)	(2,932,000)
Collection of notes and mortgages receivable	1,648,000	10,564,000	22,962,000
Net cash flow used in investing activities	(139,056,000)	(169,732,000)	(127,417,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings under credit agreements	90,000,000	175,000,000	140,000,000
Repayments under credit agreements	(80,000,000)	(140,000,000)	(135,000,000)
Proceeds from senior unsecured notes	100,000,000		175,000,000
Repayments under senior unsecured notes			(100,000,000)
Payment for extinguishment of debt			(1,233,000)
Payments of finance lease liability	(487,000)	(645,000)	(650,000)
Payments of cash dividends	(78,264,000)	(70,770,000)	(62,626,000)
Payments of debt issuance costs	(611,000)	(2,586,000)	(410,000)
Security deposits refunded	823,000	(233,000)	31,000
Payments in settlement of restricted stock units	(496,000)	(730,000)	(257,000)
Net cash flow provided by financing activities	30,758,000	52,321,000	77,980,000
Change in cash, cash equivalents and restricted cash	(15,212,000)	(30,593,000)	33,390,000
Cash, cash equivalents and restricted cash at beginning of year	26,461,000	57,054,000	23,664,000
Cash, cash equivalents and restricted cash at end of year	11,249,000	26,461,000	57,054,000
Supplemental disclosures of cash flow information Cash paid during the period for:
Interest	26,526,000	23,690,000	25,651,000
Income taxes	557,000	355,000	350,000
Environmental remediation obligations	4,252,000	4,568,000	6,355,000
Non-cash transactions
Dividends declared but not yet paid	20,576,000	19,467,000	17,332,000
Issuance of notes and mortgages receivable related to property dispositions	1,050,000	428,000	792,000
ATM Program [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net	$ (207,000)	$ 92,285,000	$ 63,187,000