Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Capital	Retained Earnings	Accumulated  Other Comprehensive Income	Treasury Stock
Beginning balance (in shares) at Dec. 31, 2021		5,173,000
Beginning balance at Dec. 31, 2021	$ 252,589	$ 5,173	$ 33,415	$ 206,875	$ 7,494	$ (368)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	44,455			44,455
Dividends paid	(69,192)			(69,192)
Change in fair value of interest rate derivatives and other	20,044				20,044
Deferred stock unit grants	450		450
Ending balance (in shares) at Sep. 30, 2022		5,173,000
Ending balance at Sep. 30, 2022	248,346	$ 5,173	33,865	182,138	27,538	(368)
Beginning balance (in shares) at Jun. 30, 2022		5,173,000
Beginning balance at Jun. 30, 2022	249,916	$ 5,173	33,865	190,101	21,145	(368)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,109			15,109
Dividends paid	(23,072)			(23,072)
Change in fair value of interest rate derivatives and other	6,393				6,393
Ending balance (in shares) at Sep. 30, 2022		5,173,000
Ending balance at Sep. 30, 2022	$ 248,346	$ 5,173	33,865	182,138	27,538	(368)
Beginning balance (in shares) at Dec. 31, 2022	5,173,450	5,173,000
Beginning balance at Dec. 31, 2022	$ 236,499	$ 5,173	33,865	172,243	25,586	(368)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	86,127			86,127
Dividends paid	(69,232)			(69,232)
Change in fair value of interest rate derivatives and other	(2,020)				(2,020)
Deferred stock unit grants	$ 450		450
Ending balance (in shares) at Sep. 30, 2023	5,173,450	5,173,000
Ending balance at Sep. 30, 2023	$ 251,824	$ 5,173	34,315	189,138	23,566	(368)
Beginning balance (in shares) at Jun. 30, 2023		5,173,000
Beginning balance at Jun. 30, 2023	265,644	$ 5,173	34,315	201,472	25,052	(368)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	10,754			10,754
Dividends paid	(23,088)			(23,088)
Change in fair value of interest rate derivatives and other	$ (1,486)				(1,486)
Ending balance (in shares) at Sep. 30, 2023	5,173,450	5,173,000
Ending balance at Sep. 30, 2023	$ 251,824	$ 5,173	$ 34,315	$ 189,138	$ 23,566	$ (368)