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)
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	86				86
Balance, end of period at Mar. 31, 2019	52,958	52,520	0	17,506	(17,207)	95	44
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)	(4,003)			(4,003)
Issuance of common stock, net of conversions	1	(1)				2
Purchase of treasury stock	2,334		2,334
Share-based compensation expense	1,629	1,629
Other comprehensive income (loss)	(835)				(835)
Reclassification adjustment to net income	332				332
Balance, end of period at Jun. 30, 2019	49,189	53,342	(2,334)	15,646	(17,604)	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)		(2,334)
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	246				246
Balance, end of period at Jun. 30, 2019	49,189	53,342	(2,334)	15,646	(17,604)	95	44
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	305				305
Balance, end of period at Mar. 31, 2020	53,396	55,062	(5,960)	23,996	(19,842)	99	41
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)	29,272
Balance, end of period at Jun. 30, 2020	61,552	56,325	(5,960)	30,528	(19,481)	99	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
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	(295)				(295)
Balance, end of period at Jun. 30, 2020	$ 61,552	$ 56,325	$ (5,960)	$ 30,528	$ (19,481)	$ 99	$ 41