Consolidated Statements of Changes in Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Capital	Retained   Earnings	Accumulated  Other Comprehensive (Loss) Income	Treasury Stock
Beginning Balance, 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	4,572			4,572
Dividends paid	(23,034)			(23,034)
Change in fair value of interest rate derivatives	25				25
Ending Balance, Shares at Mar. 31, 2020		5,173,000
Ending Balance, Value at Mar. 31, 2020	$ 235,078	$ 5,173	32,365	197,932	(24)	(368)
Beginning Balance, Shares at Dec. 31, 2020	5,173,450	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	17,882			17,882
Dividends paid	(23,050)			(23,050)
Change in fair value of interest rate derivatives	$ 5,198				5,198
Ending Balance, Shares at Mar. 31, 2021	5,173,450	5,173,000
Ending Balance, Value at Mar. 31, 2021	$ 203,258	$ 5,173	$ 32,965	$ 160,997	$ 4,491	$ (368)