CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Capital in excess of par value	Cumulative net income	Cumulative dividends	Accumulated other comprehensive income/(loss)
Balance at Dec. 31, 2020	$ 159,005	$ 138	$ 267,368	$ 680,727	$ (785,413)	$ (3,815)
Balance, Shares at Dec. 31, 2020		13,771
Shares of Beneficial Interest:
Issued	216		216
Issued (in shares)		14
Repurchased	(16)		(16)
Restricted stock-based compensation expense	947		947
Dividends	(38,585)				(38,585)
Comprehensive income:
Net income	109,166			109,166
Net income/(loss) applicable to noncontrolling interest	(334)			(334)
Unrealized net gain on cash flow hedges	4,928					4,928
Subtotal - comprehensive income	113,760			108,832		4,928
Balance at Dec. 31, 2021	235,327	$ 138	268,515	789,559	(823,998)	1,113
Balance, Shares at Dec. 31, 2021		13,785
Shares of Beneficial Interest:
Issued	177		177
Issued (in shares)		18
Restricted stock-based compensation expense	780		780
Dividends	(39,183)				(39,183)
Comprehensive income:
Net income	21,102			21,102
Unrealized net gain on cash flow hedges	10,898					10,898
Subtotal - comprehensive income	32,000			21,102		10,898
Balance at Dec. 31, 2022	229,101	$ 138	269,472	810,661	(863,181)	12,011
Balance, Shares at Dec. 31, 2022		13,803
Shares of Beneficial Interest:
Issued	146		146
Issued (in shares)		21
Restricted stock-based compensation expense	780		780
Dividends	(39,794)				(39,794)
Comprehensive income:
Net income	15,400			15,400
Unrealized net gain on cash flow hedges	(4,699)					(4,699)
Subtotal - comprehensive income	10,701			15,400		(4,699)
Balance at Dec. 31, 2023	$ 200,934	$ 138	$ 270,398	$ 826,061	$ (902,975)	$ 7,312
Balance, Shares at Dec. 31, 2023		13,824