Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Thousands		Total		Capital in Excess of Par Value	Treasury Stock	Retained Earnings (1)		Accumulated Other Comprehensive Income (Loss) (1)		Class A Common Stock Common Stock	Class B Common Stock Common Stock
Balance, beginning of period at Dec. 31, 2018		$ 56,818	[1]	$ 51,714	$ 0	$ 22,068	[1]	$ (17,101)	[1]	$ 93	$ 44
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	[1]	(3,385)				(3,385)
Issuance of common stock, net of conversions		1	[1]	(1)						2
Share-based compensation expense		807	[1]	807							0
Cash dividends on Class A Common and Class B Common	[1]	(1,177)				(1,177)
Other comprehensive income (loss)	[1]	(192)						(192)
Reclassification adjustment to net income	[1]	86						86
Balance, end of period at Mar. 31, 2019		52,958	[1]	52,520	0	17,506	[1]	(17,207)	[1]	95	44
Balance, beginning of period at Dec. 31, 2019		36,266	[1]	54,509	(5,960)	3,710	[1]	(16,132)	[1]	98	41
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	[1]	21,512				21,512
Issuance of common stock, net of conversions		0	[1]	(1)						1
Share-based compensation expense		554	[1]	554
Cash dividends on Class A Common and Class B Common	[1]	(1,226)				(1,226)
Other comprehensive income (loss)	[1]	(4,015)						(4,015)
Reclassification adjustment to net income	[1]	305						305
Balance, end of period at Mar. 31, 2020		$ 53,396	[1]	$ 55,062	$ (5,960)	$ 23,996	[1]	$ (19,842)	[1]	$ 99	$ 41

[1] As Restated