Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Capital in Excess of Par Value	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Class A Common stock Common Stock	Class B Common stock Common Stock
Balance, beginning of period at Dec. 31, 2018	$ 56,818	$ 51,714	$ 0	$ 22,068	$ (17,101)	$ 93	$ 44
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(3,385)			(3,385)
Purchase of treasury stock			0
Issuance of common stock, net of conversions	1	(1)				2
Share-based compensation expense	807	807
Cash dividends on Class A Common and Class B Common	(1,177)			(1,177)
Other comprehensive income (loss)	(192)				(192)
Reclassification adjustment to net income (loss)	86				86
Balance, end of period at Mar. 31, 2019	$ 52,958	52,520	0	17,506	(17,207)	95	44
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash Dividends on Class A Common and Class B Common per share (in dollars per share)	$ 0.085
Balance, beginning of period at Dec. 31, 2018	$ 56,818	51,714	0	22,068	(17,101)	93	44
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(6,203)
Balance, end of period at Sep. 30, 2019	42,544	54,143	(5,960)	12,231	(18,009)	95	44
Balance, beginning of period at Mar. 31, 2019	52,958	52,520	0	17,506	(17,207)	95	44
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(618)			(618)
Purchase of treasury stock			(2,334)
Issuance of common stock, net of conversions	0
Share-based compensation expense	822	822
Cash dividends on Class A Common and Class B Common	(1,242)			(1,242)
Other comprehensive income (loss)	(643)				(643)
Reclassification adjustment to net income (loss)	246				246
Balance, end of period at Jun. 30, 2019	$ 49,189	53,342	(2,334)	15,646	(17,604)	95	44
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash Dividends on Class A Common and Class B Common per share (in dollars per share)	$ 0.09
Net income (loss)	$ (2,200)			(2,200)
Purchase of treasury stock			(3,626)
Issuance of common stock, net of conversions	0	0				0
Share-based compensation expense	801	801
Cash dividends on Class A Common and Class B Common	(1,215)			(1,215)
Other comprehensive income (loss)	(654)				(654)
Reclassification adjustment to net income (loss)	249				249
Balance, end of period at Sep. 30, 2019	$ 42,544	54,143	(5,960)	12,231	(18,009)	95	44
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash Dividends on Class A Common and Class B Common per share (in dollars per share)	$ 0.09
Balance, beginning of period at Dec. 31, 2019	$ 36,266	54,509	(5,960)	3,710	(16,132)	98	41
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	21,512			21,512
Issuance of common stock, net of conversions	0	(1)				1
Share-based compensation expense	554	554
Cash dividends on Class A Common and Class B Common	(1,226)			(1,226)
Other comprehensive income (loss)	(4,015)				(4,015)
Reclassification adjustment to net income (loss)	305				305
Balance, end of period at Mar. 31, 2020	$ 53,396	55,062	(5,960)	23,996	(19,842)	99	41
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash Dividends on Class A Common and Class B Common per share (in dollars per share)	$ 0.09
Balance, beginning of period at Dec. 31, 2019	$ 36,266	54,509	(5,960)	3,710	(16,132)	98	41
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	27,262
Balance, end of period at Sep. 30, 2020	60,400	58,225	(5,960)	27,219	(19,225)	100	41
Balance, beginning of period at Mar. 31, 2020	53,396	55,062	(5,960)	23,996	(19,842)	99	41
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	7,760			7,760
Issuance of common stock, net of conversions	0
Share-based compensation expense	1,263	1,263
Cash dividends on Class A Common and Class B Common	(1,228)			(1,228)
Other comprehensive income (loss)	656				656
Reclassification adjustment to net income (loss)	(295)				(295)
Balance, end of period at Jun. 30, 2020	$ 61,552	56,325	(5,960)	30,528	(19,481)	99	41
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash Dividends on Class A Common and Class B Common per share (in dollars per share)	$ 0.09
Net income (loss)	$ (2,010)			(2,010)
Issuance of common stock, net of conversions	0	(1)				1
Share-based compensation expense	1,901	1,901
Cash dividends on Class A Common and Class B Common	(1,299)			(1,299)
Other comprehensive income (loss)	574				574
Reclassification adjustment to net income (loss)	(318)				(318)
Balance, end of period at Sep. 30, 2020	$ 60,400	$ 58,225	$ (5,960)	$ 27,219	$ (19,225)	$ 100	$ 41
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash Dividends on Class A Common and Class B Common per share (in dollars per share)	$ 0.095