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, 2017		5,173,000
Beginning Balance, Value at Dec. 31, 2017	$ 343,955	$ 5,173	$ 31,577	$ 302,543	$ 5,030	$ (368)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(9,700)			(9,700)
Dividends paid ($4.50 per common share)	(23,022)			(23,022)
Cumulative effect of change in accounting principle	0			5,156	(5,156)
Change in fair value of interest rate cap	48				48
Ending Balance, Shares at Mar. 31, 2018		5,173,000
Ending Balance, Value at Mar. 31, 2018	$ 311,281	$ 5,173	31,577	274,977	(78)	(368)
Beginning Balance, Shares at Dec. 31, 2018	5,173,450	5,173,000
Beginning Balance, Value at Dec. 31, 2018	$ 285,092	$ 5,173	31,971	248,443	(127)	(368)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	17,865			17,865
Dividends paid ($4.50 per common share)	(23,028)			(23,028)
Change in fair value of interest rate cap	$ 13				13
Ending Balance, Shares at Mar. 31, 2019	5,173,450	5,173,000
Ending Balance, Value at Mar. 31, 2019	$ 279,942	$ 5,173	$ 31,971	$ 243,280	$ (114)	$ (368)