Restatement of Previously Issued Financial Statements - Statements of Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	$ 61,552	$ 53,396	$ 36,266	$ 49,189	$ 52,958	$ 56,818	$ 36,266	$ 56,818
Net income (loss)	(2,010)	7,760	21,512	(2,200)	(618)	(3,385)	27,262	(6,203)
Issuance of common stock, net of conversions	0	0	0	0	0	1
Share-based compensation expense	1,901	1,263	554	801	822	807
Cash dividends	(1,299)	(1,228)	(1,226)	(1,215)	(1,242)	(1,177)
Other comprehensive income (loss)	574	656	(4,015)	(654)	(643)	(192)
Reclassification adjustment to net income	(318)	(295)	305	249	246	86
Balance, end of period	$ 60,400	$ 61,552	$ 53,396	$ 42,544	$ 49,189	$ 52,958	60,400	42,544
Cash Dividends on Class A Common and Class B Common per share (in dollars per share)	$ 0.095	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.085
As Previously Reported
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						$ 65,438		65,438
Net income (loss)				$ 397				(2,308)
Issuance of common stock, net of conversions								1
Purchase of treasury stock								(5,960)
Share-based compensation expense								2,430
Other comprehensive income (loss)								(1,699)
Reclassification adjustment to net income								487
Balance, end of period				54,755				$ 54,755
Cash Dividends on Class A Common and Class B Common per share (in dollars per share)								$ 0.085
Restatement Impacts
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						(8,620)		$ (8,620)
Net income (loss)				(2,597)				(3,895)
Other comprehensive income (loss)								210
Reclassification adjustment to net income								94
Balance, end of period				(12,211)				$ (12,211)
Cash Dividends on Class A Common and Class B Common per share (in dollars per share)								$ 0.085
As Restated
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						56,818		$ 56,818
Net income (loss)				(2,200)				(6,203)
Issuance of common stock, net of conversions								1
Purchase of treasury stock								(5,960)
Share-based compensation expense								2,430
Other comprehensive income (loss)								(1,489)
Reclassification adjustment to net income								581
Balance, end of period				42,544				$ 42,544
Cash Dividends on Class A Common and Class B Common per share (in dollars per share)								$ 0.085
Capital in Excess of Par Value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	$ 56,325	$ 55,062	$ 54,509	53,342	$ 52,520	51,714	54,509	$ 51,714
Issuance of common stock, net of conversions	(1)		(1)	0		(1)
Share-based compensation expense	1,901	1,263	554	801	822	807
Balance, end of period	58,225	56,325	55,062	54,143	53,342	52,520	58,225	54,143
Capital in Excess of Par Value | As Previously Reported
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						51,714		51,714
Issuance of common stock, net of conversions								(1)
Share-based compensation expense								2,430
Balance, end of period				54,143				54,143
Capital in Excess of Par Value | Restatement Impacts
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						0		0
Balance, end of period				0				0
Capital in Excess of Par Value | As Restated
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						51,714		51,714
Issuance of common stock, net of conversions								(1)
Share-based compensation expense								2,430
Balance, end of period				54,143				54,143
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(5,960)	(5,960)	(5,960)	(2,334)	0	0	(5,960)	0
Purchase of treasury stock				(3,626)	(2,334)	0
Balance, end of period	(5,960)	(5,960)	(5,960)	(5,960)	(2,334)	0	(5,960)	(5,960)
Treasury Stock | As Previously Reported
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						0		0
Purchase of treasury stock								(5,960)
Balance, end of period				(5,960)				(5,960)
Treasury Stock | Restatement Impacts
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						0		0
Balance, end of period				0				0
Treasury Stock | As Restated
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						0		0
Purchase of treasury stock								(5,960)
Balance, end of period				(5,960)				(5,960)
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	30,528	23,996	3,710	15,646	17,506	22,068	3,710	22,068
Net income (loss)	(2,010)	7,760	21,512	(2,200)	(618)	(3,385)
Cash dividends	(1,299)	(1,228)	(1,226)	(1,215)	(1,242)	(1,177)
Balance, end of period	27,219	30,528	23,996	12,231	15,646	17,506	27,219	12,231
Retained Earnings | As Previously Reported
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						30,897		30,897
Net income (loss)								(2,308)
Balance, end of period				24,955				24,955
Retained Earnings | Restatement Impacts
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						(8,829)		(8,829)
Net income (loss)								(3,895)
Balance, end of period				(12,724)				(12,724)
Retained Earnings | As Restated
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						22,068		22,068
Net income (loss)								(6,203)
Cash dividends								(3,634)
Balance, end of period				12,231				12,231
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(19,481)	(19,842)	(16,132)	(17,604)	(17,207)	(17,101)	(16,132)	(17,101)
Other comprehensive income (loss)	574	656	(4,015)	(654)	(643)	(192)
Reclassification adjustment to net income	(318)	(295)	305	249	246	86
Balance, end of period	(19,225)	(19,481)	(19,842)	(18,009)	(17,604)	(17,207)	(19,225)	(18,009)
Accumulated Other Comprehensive Income (Loss) | As Previously Reported
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						(17,310)		(17,310)
Other comprehensive income (loss)								(1,699)
Reclassification adjustment to net income								487
Balance, end of period				(18,522)				(18,522)
Accumulated Other Comprehensive Income (Loss) | Restatement Impacts
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						209		209
Other comprehensive income (loss)								210
Reclassification adjustment to net income								94
Balance, end of period				513				513
Accumulated Other Comprehensive Income (Loss) | As Restated
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						(17,101)		(17,101)
Other comprehensive income (loss)								(1,489)
Reclassification adjustment to net income								581
Balance, end of period				(18,009)				(18,009)
Class A Common stock | Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	99	99	98	95	95	93	98	93
Issuance of common stock, net of conversions	1		1	0		2
Balance, end of period	100	99	99	95	95	95	100	95
Class A Common stock | Common Stock | As Previously Reported
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						93		93
Issuance of common stock, net of conversions								2
Balance, end of period				95				95
Class A Common stock | Common Stock | Restatement Impacts
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						0		0
Balance, end of period				0				0
Class A Common stock | Common Stock | As Restated
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						93		93
Issuance of common stock, net of conversions								2
Balance, end of period				95				95
Class B Common stock | Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	41	41	41	44	44	44	41	44
Balance, end of period	$ 41	$ 41	$ 41	44	$ 44	44	$ 41	44
Class B Common stock | Common Stock | As Previously Reported
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						44		44
Balance, end of period				44				44
Class B Common stock | Common Stock | Restatement Impacts
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						0		0
Balance, end of period				0				0
Class B Common stock | Common Stock | As Restated
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period						$ 44		44
Balance, end of period				$ 44				44
Common Class A and B | As Previously Reported
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends								(3,634)
Common Class A and B | As Restated
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends								(3,634)
Common Class A and B | Retained Earnings | As Previously Reported
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends								$ (3,634)