Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common Class A and B	Total Stockholders' Equity	Total Stockholders' Equity Common Class A and B	Common Stock Class A Common Stock	Common Stock Class B Common Stock	Capital in Excess of Par Value	Treasury Stock	Retained Earnings	Retained Earnings Common Class A and B	Accumulated Other Comprehensive Income (Loss)
Balance, beginning of period at Dec. 31, 2016			$ 65,268		$ 0	$ 0	$ 75,031	$ 0	$ 6,738		$ (16,501)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 17,905		17,905						17,905
Issuance of common stock, net of conversions	0				88	48	(136)
Cash dividends			(38,000)	$ (1,162)			(27,122)		(10,878)	$ (1,162)
Other comprehensive loss			1,450								1,450
Reclassification adjustment to net income			947								947
Balance, end of period at Dec. 31, 2017			46,408		88	48	47,773	0	12,603		(14,104)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	21,784		21,784						21,784
Issuance of common stock, net of conversions	324				5	(4)	323
Stock compensation expense	3,618						3,618
Cash dividends		$ (4,658)								(4,658)
Reclassification due to adoption of ASU 2018-02	0								1,168		(1,168)
Other comprehensive loss			(2,841)								(2,841)
Reclassification adjustment to net income			803								803
Balance, end of period at Dec. 31, 2018			65,438		93	44	51,714	0	30,897		(17,310)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	(3,522)		(3,522)						(3,522)
Issuance of common stock, net of conversions	0				5	(3)	(2)
Purchase of treasury stock	(5,960)							(5,960)
Stock compensation expense	$ 2,632						2,632
Cash dividends				$ (4,851)						$ (4,851)
Other comprehensive loss			719								719
Reclassification adjustment to net income			603								603
Balance, end of period at Dec. 31, 2019			$ 55,059		$ 98	$ 41	$ 54,344	$ (5,960)	$ 22,524		$ (15,988)