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, 2017	$ 67	$ 9	$ 62,675	$ 151,608	$ (34,894)	$ 179,465
Balance, shares at Dec. 31, 2017	6,694	898
Net income (loss)	$ 0	$ 0	0	13,690	0	13,690
Conversion of shares from Class B to Class A	$ 0	$ 0	0	0	0	0
Conversion of shares from Class B to Class A (in shares)	12	(12)
Issuance of restricted stock	$ 0	$ 0	0	0	0	0
Issuance of restricted stock (in shares)	27	37
Forfeiture of restricted stock	$ 0	$ 0	0	0	0	0
Forfeiture of restricted stock (in shares)	(1)	0
Dividends declared per common share	$ 0	$ 0	0	(8,609)	0	(8,609)
Compensation expense related to restricted stock awards	0	0	2,201	0	0	2,201
Purchase of shares held in treasury	0	0	0	0	(2,000)	(2,000)
401(k) plan contribution	0	0	(81)	0	333	252
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	13,279	0	13,279
Conversion of shares from Class B to Class A	$ 0	$ 0	0	0	0	0
Conversion of shares from Class B to Class A (in shares)	13	(13)
Issuance of restricted stock	$ 1	$ 0	0	0	0	1
Issuance of restricted stock (in shares)	29	44
Forfeiture of restricted stock	$ 0	$ 0	0	0	0	0
Forfeiture of restricted stock (in shares)	(3)	0
Dividends declared per common share	$ 0	$ 0	0	(7,146)	0	(7,146)
Compensation expense related to restricted stock awards	0	0	2,129	0	0	2,129
Purchase of shares held in treasury	0	0	0	0	(1,172)	(1,172)
401(k) plan contribution	0	0	(113)	0	375	262
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	(1,913)	0	(1,913)
Conversion of shares from Class B to Class A	$ 0	$ 0	0	0	0	0
Conversion of shares from Class B to Class A (in shares)	16	(16)
Forfeiture of restricted stock	$ 0	$ 0	0	0	0	0
Forfeiture of restricted stock (in shares)	(2)
Dividends declared per common share	$ 0	0	0	(1,919)	0	(1,919)
Compensation expense related to restricted stock awards	0	0	2,221	0	0	2,221
Purchase of shares held in treasury	0	0	0	0	(449)	(449)
401(k) plan contribution	0	0	(132)	0	382	250
Balance at Dec. 31, 2020	$ 68	$ 9	$ 68,900	$ 158,990	$ (37,425)	$ 190,542
Balance, shares at Dec. 31, 2020	6,785	938