CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Class A Common Stock Common Stock [Member]	Class A Common Stock	Class B Common Stock Common Stock [Member]	Class B Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Total
Balance at Dec. 31, 2019	$ 68		$ 9		$ 66,811	$ 162,822	$ (37,358)	$ 192,352
Balance, shares at Dec. 31, 2019	6,771	6,771	954	954
Net income (loss)	$ 0		$ 0		0	1,680	0	1,680
Dividends declared per common share	0		0		0	(1,919)	0	(1,919)
Compensation expense related to restricted stock awards	0		0		569	0	0	569
Purchase of shares held in treasury	0		0		0	0	(20)	(20)
401(k) plan contribution	0		0		(131)	0	382	251
Balance at Mar. 31, 2020	$ 68		$ 9		67,249	162,583	(36,996)	192,913
Balance, shares at Mar. 31, 2020	6,771		954
Balance at Dec. 31, 2019	$ 68		$ 9		66,811	162,822	(37,358)	192,352
Balance, shares at Dec. 31, 2019	6,771	6,771	954	954
Net income (loss)								(4,181)
Balance at Sep. 30, 2020	$ 68		$ 9		68,479	156,722	(37,039)	188,239
Balance, shares at Sep. 30, 2020	6,769		954
Balance at Dec. 31, 2019	$ 68		$ 9		66,811	162,822	(37,358)	192,352
Balance, shares at Dec. 31, 2019	6,771	6,771	954	954
Issuance of restricted stock (in shares)		0		0
Forfeiture of restricted stock (in shares)		(2)		0
Balance at Dec. 31, 2020	$ 68		$ 9		68,900	158,990	(37,425)	190,542	[1]
Balance, shares at Dec. 31, 2020	6,785	6,785	938	938
Balance at Mar. 31, 2020	$ 68		$ 9		67,249	162,583	(36,996)	192,913
Balance, shares at Mar. 31, 2020	6,771		954
Net income (loss)	$ 0		$ 0		0	(4,911)	0	(4,911)
Forfeiture of restricted stock	$ 0		$ 0		0	0	0	0
Forfeiture of restricted stock (in shares)	(2)		0
Compensation expense related to restricted stock awards	$ 0		$ 0		612	0	0	612
Purchase of shares held in treasury	0		0		0	0	(21)	(21)
Balance at Jun. 30, 2020	$ 68		$ 9		67,861	157,672	(37,017)	188,593
Balance, shares at Jun. 30, 2020	6,769		954
Net income (loss)	$ 0		$ 0		0	(950)	0	(950)
Compensation expense related to restricted stock awards	0		0		618	0	0	618
Purchase of shares held in treasury	0		0		0	0	(22)	(22)
Balance at Sep. 30, 2020	$ 68		$ 9		68,479	156,722	(37,039)	188,239
Balance, shares at Sep. 30, 2020	6,769		954
Balance at Dec. 31, 2020	$ 68		$ 9		68,900	158,990	(37,425)	190,542	[1]
Balance, shares at Dec. 31, 2020	6,785	6,785	938	938
Net income (loss)	$ 0		$ 0		0	758	0	758
Compensation expense related to restricted stock awards	0		0		343	0	0	343
401(k) plan contribution	0		0		(200)	0	421	221
Balance at Mar. 31, 2021	$ 68		$ 9		69,043	159,748	(37,004)	191,864
Balance, shares at Mar. 31, 2021	6,785		938
Balance at Dec. 31, 2020	$ 68		$ 9		68,900	158,990	(37,425)	190,542	[1]
Balance, shares at Dec. 31, 2020	6,785	6,785	938	938
Net income (loss)								7,465
Balance at Sep. 30, 2021	$ 68		$ 9		69,748	164,543	(37,004)	197,364
Balance, shares at Sep. 30, 2021	6,785	6,785	938	938
Balance at Mar. 31, 2021	$ 68		$ 9		69,043	159,748	(37,004)	191,864
Balance, shares at Mar. 31, 2021	6,785		938
Net income (loss)	$ 0		$ 0		0	3,253	0	3,253
Dividends declared per common share	0		0		0	(956)	0	(956)
Compensation expense related to restricted stock awards	0		0		357	0	0	357
Balance at Jun. 30, 2021	$ 68		$ 9		69,400	162,045	(37,004)	194,518
Balance, shares at Jun. 30, 2021	6,785		938
Net income (loss)	$ 0		$ 0		0	3,454	0	3,454
Dividends declared per common share	0		0		0	(956)	0	(956)
Compensation expense related to restricted stock awards	0		0		348	0	0	348
Balance at Sep. 30, 2021	$ 68		$ 9		$ 69,748	$ 164,543	$ (37,004)	$ 197,364
Balance, shares at Sep. 30, 2021	6,785	6,785	938	938

[1] The balance sheet at December 31, 2020 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements.