Earnings Per Share - EPS Calculation (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($) class_of_stock $ / shares shares	Mar. 31, 2021 USD ($) $ / shares shares
Earnings Per Share [Abstract]
Number of classes of common stock | class_of_stock	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	$ 36,184	$ 62,129
Undistributed earnings	36,184	62,129
Allocation of net earnings:
Undistributed earnings	36,184	62,129
Net earnings	36,184	62,129
Class A
Numerator for Basic and Diluted Earnings Per Share:
Net earnings	35,161	60,372
Dividends	0	0
Undistributed earnings	35,161	60,372
Allocation of net earnings:
Dividends	0	0
Undistributed earnings	35,161	60,372
Net earnings	$ 35,161	$ 60,372
Denominator:
Basic earnings per share - weighted-average shares (in shares) | shares	3,436,000	3,436,000
Effect of dilutive stock options (in shares) | shares	0	0
Diluted earnings per share - adjusted weighted-average shares for assumed conversions (in shares) | shares	3,436,000	3,436,000
Basic earnings per share (in dollars per share) | $ / shares	$ 10.23	$ 17.57
Diluted earnings per share (in dollars per share) | $ / shares	$ 10.23	$ 17.57
Class B
Numerator for Basic and Diluted Earnings Per Share:
Net earnings	$ 1,023	$ 1,757
Dividends	0	0
Undistributed earnings	1,023	1,757
Allocation of net earnings:
Dividends	0	0
Undistributed earnings	1,023	1,757
Net earnings	$ 1,023	$ 1,757
Denominator:
Basic earnings per share - weighted-average shares (in shares) | shares	200,000	200,000
Effect of dilutive stock options (in shares) | shares	0	0
Diluted earnings per share - adjusted weighted-average shares for assumed conversions (in shares) | shares	200,000	200,000
Basic earnings per share (in dollars per share) | $ / shares	$ 5.12	$ 8.79
Diluted earnings per share (in dollars per share) | $ / shares	$ 5.12	$ 8.79