Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Voting Common Stock [Member] Common Stock [Member]	Voting Common Stock [Member]	Nonvoting Common Stock [Member] Common Stock [Member]	Nonvoting Common Stock [Member]	Paid-In Capital [Member]	Treasury Stock Voting [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]	Total
Balance at Dec. 31, 2018	$ 216		$ 95		$ 1,019,988	$ (9,592)	$ (695,521)	$ (17,620)	$ 297,566
Balance, shares at Dec. 31, 2018	21,582,000		9,506,000			154,000
Net income							89,755		89,755
Other comprehensive income (loss)								(37,294)	(37,294)
Comprehensive income (loss)									52,461
Balance at Dec. 31, 2019	$ 216		$ 95		1,019,988	$ (9,592)	(605,766)	(54,914)	350,027
Balance, shares at Dec. 31, 2019	21,582,000	21,581,572	9,506,000	9,505,673		154,000
Net income							93,093		93,093
Other comprehensive income (loss)								(17,058)	(17,058)
Comprehensive income (loss)									76,035
Common dividends paid ($7.00 per share)							(216,529)		(216,529)
Balance at Dec. 31, 2020	$ 216		$ 95		$ 1,019,988	$ (9,592)	$ (729,202)	$ (71,972)	$ 209,533
Balance, shares at Dec. 31, 2020	21,582,000	21,581,572	9,506,000	9,505,673		154,000