Schedule II Valuation and qualifying accounts (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Allowance for doubtful accounts - Tenant rent receivables
Movement in valuation and qualifying accounts
Balance at beginning of year	$ 17,000	$ 533,000	$ 505,000
Additions (Decreases) charged to costs and expenses	(9,000)	(38,000)	157,000
Deductions		(478,000)	(129,000)
Balance at end of year	8,000	17,000	$ 533,000
Allowance for doubtful accounts - Allowance for credit losses
Movement in valuation and qualifying accounts
Balance at beginning of year	4,237,000
Additions (Decreases) charged to costs and expenses	$ (4,237,000)	4,237,000
Balance at end of year		$ 4,237,000