Consolidated Statements of Shareholders' Equity - USD ($)	Common Stock [Member] Series A	Common Stock [Member] Series B	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock Series A	Treasury Stock	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Total
Beginning Balance at Dec. 31, 2017			$ 232,000	$ 494,989,000		$ (11,302,000)	$ (24,932,000)	$ (361,288,000)	$ 97,699,000
Beginning Balance, Shares Common Stock at Dec. 31, 2017	20,700,292	2,469,755
Beginning Balance, Treasury Stock at Dec. 31, 2017					(1,430,961)
Net income (loss)								(4,548,000)	(4,548,000)
Other comprehensive income							315,000		315,000
Shares repurchased, shares					(160,180)
Shares repurchased						(825,000)			(825,000)
Issuance of shares for restricted stock units, shares	151,236
Issuance of shares for restricted stock units			1,000	(1,000)
Share-based compensation				720,000					720,000
Conversion of Series B to Series A, shares	120	(120)
Dividends declared								(3,564,000)	(3,564,000)
Ending Balance at Jun. 30, 2018			233,000	495,708,000		(12,127,000)	(24,617,000)	(369,400,000)	89,797,000
Ending Balance, Shares Common Stock at Jun. 30, 2018	20,851,648	2,469,635
Ending Balance, Shares Treasury Stock at Jun. 30, 2018					(1,591,141)
Beginning Balance at Mar. 31, 2018			233,000	495,605,000		(11,857,000)	(24,774,000)	(367,083,000)	92,124,000
Beginning Balance, Shares Common Stock at Mar. 31, 2018	20,817,514	2,469,635
Beginning Balance, Treasury Stock at Mar. 31, 2018					(1,539,739)
Net income (loss)								(534,000)	(534,000)
Other comprehensive income							157,000		157,000
Shares repurchased, shares					(51,402)
Shares repurchased						(270,000)			(270,000)
Issuance of shares for restricted stock units, shares	34,134
Share-based compensation				103,000					103,000
Dividends declared								(1,783,000)	(1,783,000)
Ending Balance at Jun. 30, 2018			233,000	495,708,000		(12,127,000)	(24,617,000)	(369,400,000)	89,797,000
Ending Balance, Shares Common Stock at Jun. 30, 2018	20,851,648	2,469,635
Ending Balance, Shares Treasury Stock at Jun. 30, 2018					(1,591,141)
Beginning Balance at Dec. 31, 2018			233,000	494,389,000		(12,601,000)	(37,641,000)	(393,582,000)	50,798,000
Beginning Balance, Shares Common Stock at Dec. 31, 2018	20,854,728	2,469,555
Beginning Balance, Treasury Stock at Dec. 31, 2018					(1,697,370)
Net income (loss)								14,393,000	14,393,000
Other comprehensive income							125,000		125,000
Shares repurchased, shares					(131,613)
Shares repurchased						(527,000)			(527,000)
Conversion of Series B to Series A, shares	43	(43)
Dividends declared								(3,436,000)	(3,436,000)
Ending Balance at Jun. 30, 2019			233,000	494,389,000	$ (1,828,983)	(13,128,000)	(37,516,000)	(382,625,000)	61,353,000
Ending Balance, Shares Common Stock at Jun. 30, 2019	20,854,771	2,469,512
Ending Balance, Shares Treasury Stock at Jun. 30, 2019					(1,828,983)
Beginning Balance at Mar. 31, 2019			233,000	494,389,000		(12,941,000)	(37,578,000)	(397,437,000)	46,666,000
Beginning Balance, Shares Common Stock at Mar. 31, 2019	20,854,739	2,469,544
Beginning Balance, Treasury Stock at Mar. 31, 2019					(1,780,899)
Net income (loss)								16,528,000	16,528,000
Other comprehensive income							62,000		62,000
Shares repurchased, shares					(48,084)
Shares repurchased						(187,000)			(187,000)
Conversion of Series B to Series A, shares	32	(32)
Dividends declared								(1,716,000)	(1,716,000)
Ending Balance at Jun. 30, 2019			$ 233,000	$ 494,389,000	$ (1,828,983)	$ (13,128,000)	$ (37,516,000)	$ (382,625,000)	$ 61,353,000
Ending Balance, Shares Common Stock at Jun. 30, 2019	20,854,771	2,469,512
Ending Balance, Shares Treasury Stock at Jun. 30, 2019					(1,828,983)