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, 2016	$ 66	$ 8	$ 59,557	$ 108,733	$ (33,382)	$ 134,982
Balance, shares at Dec. 31, 2016	6,638	878
Net income	$ 0	$ 0		54,717		54,717
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)	17	(17)
Issuance of restricted stock	$ 0	$ 1	(1)	0	0	0
Issuance of restricted stock (in shares)	19	29
Forfeiture of restricted stock	$ 0	$ 0
Forfeiture of restricted stock (in shares)	(1)
Net proceeds from exercised options	$ 1	$ 0	826		(826)	1
Net proceeds from exercised options (in shares)	21	8
Dividends declared per common share	$ 0	$ 0		(11,842)		(11,842)
Compensation expense related to restricted stock awards	0	0	2,279	0	0	2,279
Purchase of shares held in treasury	0	0	0	0	(946)	(946)
401(k) plan contribution	0	0	14	0	260	274
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	$ 0	$ 0		13,690		13,690
Conversion of shares from Class B to Class A	$ 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
Forfeiture of restricted stock (in shares)	(1)
Dividends declared per common share	$ 0	$ 0		(8,609)		(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	(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	$ 0	$ 0		13,279		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
Forfeiture of restricted stock (in shares)	(3)
Dividends declared per common share	$ 0	0		(7,146)		(7,146)
Compensation expense related to restricted stock awards	0	0	2,129			2,129
Purchase of shares held in treasury	0	0			(1,172)	(1,172)
401(k) plan contribution	0	0	(113)		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