Condensed Consolidated Statements of Changes in Equity - USD ($) $ 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, 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, net	93		93
Issued, net (in shares)		16
Restricted stock-based compensation expense	431		431
Dividends and dividend equivalents	(19,517)				(19,517)
Comprehensive income:
Net income	10,623			10,623
Unrealized net gain/(loss) on cash flow hedges	7,689					7,689
Subtotal - comprehensive income	18,312			10,623		7,689
Balance at Jun. 30, 2022	234,646	$ 138	269,039	800,182	(843,515)	8,802
Balance, Shares at Jun. 30, 2022		13,801
Balance at Mar. 31, 2022	236,974	$ 138	268,792	794,964	(833,717)	6,797
Balance, Shares at Mar. 31, 2022		13,786
Shares of Beneficial Interest:
Issued, net	39		39
Issued, net (in shares)		15
Restricted stock-based compensation expense	208		208
Dividends and dividend equivalents	(9,798)				(9,798)
Comprehensive income:
Net income	5,218			5,218
Unrealized net gain/(loss) on cash flow hedges	2,005					2,005
Subtotal - comprehensive income	7,223			5,218		2,005
Balance at Jun. 30, 2022	234,646	$ 138	269,039	800,182	(843,515)	8,802
Balance, Shares at Jun. 30, 2022		13,801
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, net	75		75
Issued, net (in shares)		19
Restricted stock-based compensation expense	376		376
Dividends and dividend equivalents	(19,820)				(19,820)
Comprehensive income:
Net income	7,935			7,935
Unrealized net gain/(loss) on cash flow hedges	(1,032)					(1,032)
Subtotal - comprehensive income	6,903			7,935		(1,032)
Balance at Jun. 30, 2023	216,635	$ 138	269,923	818,596	(883,001)	10,979
Balance, Shares at Jun. 30, 2023		13,822
Balance at Mar. 31, 2023	222,170	$ 138	269,698	815,120	(873,050)	10,264
Balance, Shares at Mar. 31, 2023		13,804
Shares of Beneficial Interest:
Issued, net	37		37
Issued, net (in shares)		18
Restricted stock-based compensation expense	188		188
Dividends and dividend equivalents	(9,951)				(9,951)
Comprehensive income:
Net income	3,476			3,476
Unrealized net gain/(loss) on cash flow hedges	715					715
Subtotal - comprehensive income	4,191			3,476		715
Balance at Jun. 30, 2023	$ 216,635	$ 138	$ 269,923	$ 818,596	$ (883,001)	$ 10,979
Balance, Shares at Jun. 30, 2023		13,822