Earnings Per Share - EPS Calculation (Details) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($) class_of_stock $ / shares shares	Jun. 30, 2022 USD ($) $ / shares shares	Jun. 30, 2023 USD ($) class_of_stock $ / shares shares	Jun. 30, 2022 USD ($) $ / shares shares
Earnings Per Share [Abstract]
Number of classes of common stock | class_of_stock	2		2
Share-based compensation awards outstanding that could be redeemed for shares of common stock (shares) | shares			0
Numerator for Basic and Diluted Earnings Per Share:
Net earnings	$ 29,634	$ 96,527	$ 41,938	$ 194,089
Undistributed earnings	29,634	96,527	41,938	194,089
Allocation of net earnings:
Undistributed earnings	29,634	96,527	41,938	194,089
Net earnings	29,634	96,527	41,938	194,089
Class A
Numerator for Basic and Diluted Earnings Per Share:
Net earnings	28,796	93,797	40,752	188,600
Dividends	0	0	0	0
Undistributed earnings	28,796	93,797	40,752	188,600
Allocation of net earnings:
Dividends	0	0	0	0
Undistributed earnings	28,796	93,797	40,752	188,600
Net earnings	$ 28,796	$ 93,797	$ 40,752	$ 188,600
Denominator:
Basic earnings per share - weighted-average shares (in shares) | shares	3,436,000	3,436,000	3,436,000	3,436,000
Effect of dilutive stock options (in shares) | shares	0	0	0	0
Diluted earnings per share - adjusted weighted-average shares for assumed conversions (in shares) | shares	3,436,000	3,436,000	3,436,000	3,436,000
Basic earnings per share (in dollars per share) | $ / shares	$ 8.38	$ 27.30	$ 11.86	$ 54.89
Diluted earnings per share (in dollars per share) | $ / shares	$ 8.38	$ 27.30	$ 11.86	$ 54.89
Class B
Numerator for Basic and Diluted Earnings Per Share:
Net earnings	$ 838	$ 2,730	$ 1,186	$ 5,489
Dividends	0	0	0	0
Undistributed earnings	838	2,730	1,186	5,489
Allocation of net earnings:
Dividends	0	0	0	0
Undistributed earnings	838	2,730	1,186	5,489
Net earnings	$ 838	$ 2,730	$ 1,186	$ 5,489
Denominator:
Basic earnings per share - weighted-average shares (in shares) | shares	200,000	200,000	200,000	200,000
Effect of dilutive stock options (in shares) | shares	0	0	0	0
Diluted earnings per share - adjusted weighted-average shares for assumed conversions (in shares) | shares	200,000	200,000	200,000	200,000
Basic earnings per share (in dollars per share) | $ / shares	$ 4.19	$ 13.65	$ 5.93	$ 27.44
Diluted earnings per share (in dollars per share) | $ / shares	$ 4.19	$ 13.65	$ 5.93	$ 27.44