Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Voting Common Stock [Member]	Nonvoting Common Stock [Member]	Paid-In Capital [Member]	Treasury Stock [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 (loss) income					76,743
Other comprehensive income (loss)						(13,052)
Comprehensive (loss) income							63,691
Balance at Jun. 30, 2019	$ 216	$ 95	1,019,988	$ (9,592)	(618,778)	(30,672)	361,257
Balance, shares at Jun. 30, 2019	21,582,000	9,506,000		154,000
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 (loss) income							82,990
Other comprehensive income (loss)							(29,313)
Comprehensive (loss) income							53,677
Balance at Sep. 30, 2019	$ 216	$ 95	1,019,988	$ (9,592)	(612,531)	(46,933)	351,243
Balance, shares at Sep. 30, 2019	21,582,000	9,506,000		154,000
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
Other comprehensive income (loss)						(37,294)
Balance at Dec. 31, 2019	$ 216	$ 95	1,019,988	$ (9,592)	(605,766)	(54,914)	350,027
Balance, shares at Dec. 31, 2019	21,581,572	9,505,673		154,000
Balance at Jun. 30, 2019	$ 216	$ 95	1,019,988	$ (9,592)	(618,778)	(30,672)	361,257
Balance, shares at Jun. 30, 2019	21,582,000	9,506,000		154,000
Net (loss) income					6,247		6,247
Other comprehensive income (loss)						(16,261)	(16,261)
Comprehensive (loss) income							(10,014)
Balance at Sep. 30, 2019	$ 216	$ 95	1,019,988	$ (9,592)	(612,531)	(46,933)	351,243
Balance, shares at Sep. 30, 2019	21,582,000	9,506,000		154,000
Net (loss) income					6,765
Other comprehensive income (loss)						(7,981)
Comprehensive (loss) income							(1,216)
Balance at Dec. 31, 2019	$ 216	$ 95	1,019,988	$ (9,592)	(605,766)	(54,914)	350,027
Balance, shares at Dec. 31, 2019	21,581,572	9,505,673		154,000
Net (loss) income					(47,777)
Other comprehensive income (loss)						14,111
Comprehensive (loss) income							(33,666)
Common dividends paid ($5.50 per share)					(170,130)		(170,130)
Balance at Jun. 30, 2020	$ 216	$ 95	1,019,988	$ (9,592)	(823,673)	(40,803)	146,231
Balance, shares at Jun. 30, 2020	21,582,000	9,506,000		154,000
Balance at Dec. 31, 2019	$ 216	$ 95	1,019,988	$ (9,592)	(605,766)	(54,914)	350,027
Balance, shares at Dec. 31, 2019	21,581,572	9,505,673		154,000
Net (loss) income							3,395
Other comprehensive income (loss)						6,891	6,891
Comprehensive (loss) income							10,286
Balance at Sep. 30, 2020	$ 216	$ 95	1,019,988	$ (9,592)	(772,501)	(48,023)	190,183
Balance, shares at Sep. 30, 2020	21,581,572	9,505,673		154,000
Balance at Jun. 30, 2020	$ 216	$ 95	1,019,988	$ (9,592)	(823,673)	(40,803)	146,231
Balance, shares at Jun. 30, 2020	21,582,000	9,506,000		154,000
Net (loss) income					51,172		51,172
Other comprehensive income (loss)						(7,220)	(7,220)
Comprehensive (loss) income							43,952
Balance at Sep. 30, 2020	$ 216	$ 95	$ 1,019,988	$ (9,592)	$ (772,501)	$ (48,023)	$ 190,183
Balance, shares at Sep. 30, 2020	21,581,572	9,505,673		154,000