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	29,346			29,346
Dividends paid	(46,120)			(46,120)
Change in fair value of interest rate derivatives and other	13,651				13,651
Deferred stock unit grants	450		450
Ending balance (in shares) at Jun. 30, 2022		5,173,000
Ending balance at Jun. 30, 2022	249,916	$ 5,173	33,865	190,101	21,145	(368)
Beginning balance (in shares) at Mar. 31, 2022		5,173,000
Beginning balance at Mar. 31, 2022	255,788	$ 5,173	33,415	198,347	19,221	(368)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	14,814			14,814
Dividends paid	(23,060)			(23,060)
Change in fair value of interest rate derivatives and other	1,924				1,924
Deferred stock unit grants	450		450
Ending balance (in shares) at Jun. 30, 2022		5,173,000
Ending balance at Jun. 30, 2022	$ 249,916	$ 5,173	33,865	190,101	21,145	(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	75,373			75,373
Dividends paid	(46,144)			(46,144)
Change in fair value of interest rate derivatives and other	(534)				(534)
Deferred stock unit grants	$ 450		450
Ending balance (in shares) at Jun. 30, 2023	5,173,450	5,173,000
Ending balance at Jun. 30, 2023	$ 265,644	$ 5,173	34,315	201,472	25,052	(368)
Beginning balance (in shares) at Mar. 31, 2023		5,173,000
Beginning balance at Mar. 31, 2023	221,009	$ 5,173	33,865	160,397	21,942	(368)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	64,147			64,147
Dividends paid	(23,072)			(23,072)
Change in fair value of interest rate derivatives and other	3,110				3,110
Deferred stock unit grants	$ 450		450
Ending balance (in shares) at Jun. 30, 2023	5,173,450	5,173,000
Ending balance at Jun. 30, 2023	$ 265,644	$ 5,173	$ 34,315	$ 201,472	$ 25,052	$ (368)