Consolidated Statements of Changes in Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Capital	Retained Earnings	Accumulated  Other Comprehensive Income (Loss)	Treasury Stock
Beginning Balance, Shares at Dec. 31, 2020		5,173,000
Beginning Balance, Value at Dec. 31, 2020	$ 203,228	$ 5,173	$ 32,965	$ 166,165	$ (707)	$ (368)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	43,780			43,780
Dividends paid	(46,100)			(46,100)
Change in fair value of interest rate derivatives and other	4,447				4,447
Deferred stock unit grants	450		450
Ending Balance, Shares at Jun. 30, 2021		5,173,000
Ending Balance, Value at Jun. 30, 2021	205,805	$ 5,173	33,415	163,845	3,740	(368)
Beginning Balance, Shares at Mar. 31, 2021		5,173,000
Beginning Balance, Value at Mar. 31, 2021	203,258	$ 5,173	32,965	160,997	4,491	(368)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	25,898			25,898
Dividends paid	(23,050)			(23,050)
Change in fair value of interest rate derivatives and other	(751)				(751)
Deferred stock unit grants	450		450
Ending Balance, Shares at Jun. 30, 2021		5,173,000
Ending Balance, Value at Jun. 30, 2021	$ 205,805	$ 5,173	33,415	163,845	3,740	(368)
Beginning Balance, Shares at Dec. 31, 2021	5,173,450	5,173,000
Beginning Balance, Value 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, Shares at Jun. 30, 2022	5,173,450	5,173,000
Ending Balance, Value at Jun. 30, 2022	$ 249,916	$ 5,173	33,865	190,101	21,145	(368)
Beginning Balance, Shares at Mar. 31, 2022		5,173,000
Beginning Balance, Value 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, Shares at Jun. 30, 2022	5,173,450	5,173,000
Ending Balance, Value at Jun. 30, 2022	$ 249,916	$ 5,173	$ 33,865	$ 190,101	$ 21,145	$ (368)