CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Class A Common Stock	Class B Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Total
Balance at Dec. 31, 2018	$ 67	$ 9	$ 64,795	$ 156,689	$ (36,561)	$ 184,999
Balance, shares at Dec. 31, 2018	6,732	923
Net income (loss)	$ 0	$ 0	0	1,370	0	1,370
Dividends declared per common share	0	0	0	(1,784)	0	(1,784)
Compensation expense related to restricted stock awards	0	0	559	0	0	559
Purchase of shares held in treasury	0	0	0	0	(80)	(80)
401(k) plan contribution	0	0	(113)	0	375	262
Balance at Mar. 31, 2019	$ 67	$ 9	65,241	156,275	(36,266)	185,326
Balance, shares at Mar. 31, 2019	6,732	923
Balance at Dec. 31, 2018	$ 67	$ 9	64,795	156,689	(36,561)	184,999
Balance, shares at Dec. 31, 2018	6,732	923
Net income (loss)						9,438
Balance at Sep. 30, 2019	$ 67	$ 9	66,338	160,778	(36,789)	190,403
Balance, shares at Sep. 30, 2019	6,730	923
Balance at Dec. 31, 2018	$ 67	$ 9	64,795	156,689	(36,561)	184,999
Balance, shares at Dec. 31, 2018	6,732	923
Issuance of restricted stock (in shares)	29	44
Forfeiture of restricted stock (in shares)	(3)	0
Balance at Dec. 31, 2019	$ 68	$ 9	66,811	162,822	(37,358)	192,352
Balance, shares at Dec. 31, 2019	6,771	954
Balance at Mar. 31, 2019	$ 67	$ 9	65,241	156,275	(36,266)	185,326
Balance, shares at Mar. 31, 2019	6,732	923
Net income (loss)	$ 0	$ 0	0	4,734	0	4,734
Dividends declared per common share	0	0	0	(1,784)	0	(1,784)
Compensation expense related to restricted stock awards	0	0	565	0	0	565
Purchase of shares held in treasury	0	0	0	0	(247)	(247)
Balance at Jun. 30, 2019	$ 67	$ 9	65,806	159,225	(36,513)	188,594
Balance, shares at Jun. 30, 2019	6,732	923
Net income (loss)	$ 0	$ 0	0	3,334	0	3,334
Forfeiture of restricted stock	$ 0	$ 0	0	0	0	0
Forfeiture of restricted stock (in shares)	(2)	0
Dividends declared per common share	$ 0	$ 0	0	(1,781)	0	(1,781)
Compensation expense related to restricted stock awards	0	0	532	0	0	532
Purchase of shares held in treasury	0	0	0	0	(276)	(276)
Balance at Sep. 30, 2019	$ 67	$ 9	66,338	160,778	(36,789)	190,403
Balance, shares at Sep. 30, 2019	6,730	923
Balance at Dec. 31, 2019	$ 68	$ 9	66,811	162,822	(37,358)	192,352
Balance, shares at Dec. 31, 2019	6,771	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	954
Net income (loss)						(4,181)
Forfeiture of restricted stock (in shares)	(2)	0
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 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