Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Treasury Stock
Beginning Balance (in shares) at Dec. 31, 2019		5,173,000
Beginning Balance, Value at Dec. 31, 2019	$ 253,515	$ 5,173	$ 32,365	$ 216,394	$ (49)	$ (368)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	41,939			41,939
Dividends paid ($18.00 per common share)	(92,168)			(92,168)
Change in fair value of interest rate derivatives and other	(658)				(658)
Deferred stock unit grants	600		600
Ending Balance (in shares) at Dec. 31, 2020		5,173,000
Ending 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	132,930			132,930
Dividends paid ($18.00 per common share)	(92,220)			(92,220)
Change in fair value of interest rate derivatives and other	8,201				8,201
Deferred stock unit grants	$ 450		450
Ending Balance (in shares) at Dec. 31, 2021	5,173,450	5,173,000
Ending 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	57,632			57,632
Dividends paid ($18.00 per common share)	(92,264)			(92,264)
Change in fair value of interest rate derivatives and other	18,092				18,092
Deferred stock unit grants	$ 450		450
Ending Balance (in shares) at Dec. 31, 2022	5,173,450	5,173,000
Ending Balance, Value at Dec. 31, 2022	$ 236,499	$ 5,173	$ 33,865	$ 172,243	$ 25,586	$ (368)