Unaudited Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Common Stock Class A Common Stock	Common Stock Class B Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance, beginning of period at Dec. 31, 2020	$ 300,624	$ 5,490	$ 1,568	$ 10,895	$ 294,270	$ (11,599)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	1,015	92		923
Conversion of Class B to Class A shares	0	1	(1)
Net income	8,961				8,961
Cash dividends on Class A and Class B common stock	(1,374)				(1,374)
Reclassification adjustment to net income, net of tax	143					143
Balance, end of period at Mar. 31, 2021	309,369	5,583	1,567	11,818	301,857	(11,456)
Balance, beginning of period at Dec. 31, 2020	300,624	5,490	1,568	10,895	294,270	(11,599)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,466
Balance, end of period at Jun. 30, 2021	315,727	5,595	1,567	12,928	306,950	(11,313)
Balance, beginning of period at Mar. 31, 2021	309,369	5,583	1,567	11,818	301,857	(11,456)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	1,122	12		1,110
Net income	6,505				6,505
Cash dividends on Class A and Class B common stock	(1,412)				(1,412)
Reclassification adjustment to net income, net of tax	143					143
Balance, end of period at Jun. 30, 2021	315,727	5,595	1,567	12,928	306,950	(11,313)
Balance, beginning of period at Dec. 31, 2021	352,116	5,616	1,567	16,331	336,778	(8,176)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	1,123	145		978
Conversion of Class B to Class A shares	0	1	(1)
Net income	12,582				12,582
Cash dividends on Class A and Class B common stock	(1,445)				(1,445)
Reclassification adjustment to net income, net of tax	118					118
Balance, end of period at Mar. 31, 2022	364,494	5,762	1,566	17,309	347,915	(8,058)
Balance, beginning of period at Dec. 31, 2021	352,116	5,616	1,567	16,331	336,778	(8,176)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	49,762
Balance, end of period at Jun. 30, 2022	402,603	5,769	1,566	19,634	383,574	(7,940)
Balance, beginning of period at Mar. 31, 2022	364,494	5,762	1,566	17,309	347,915	(8,058)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	2,332	7		2,325
Net income	37,180				37,180
Cash dividends on Class A and Class B common stock	(1,521)				(1,521)
Reclassification adjustment to net income, net of tax	118					118
Balance, end of period at Jun. 30, 2022	$ 402,603	$ 5,769	$ 1,566	$ 19,634	$ 383,574	$ (7,940)