Earnings Per Share (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) $ / shares shares	Mar. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2020
Class A common stock
Income available to stockholders (Basic EPS:)
Allocated net income (numerator) | $	$ 72,964	$ 58,840
Weighted shares (denominator) | shares	46,188,860	46,188,789
Per-share amount (in dollars per share) | $ / shares	$ 1.58	$ 1.27
Dilutive effect of stock-based awards
Allocated net income (numerator) | $	$ 0	$ 0
Weighted shares (denominator) | shares	26,298	34,761
Assumed conversion of Class B shares
Allocated net income (numerator) | $	$ 602	$ 486
Weighted shares (denominator) | shares	6,100,800	6,100,800
Income available to stockholders on equivalent shares (Diluted EPS:)
Allocated net income (numerator) | $	$ 73,566	$ 59,326
Weighted shares (denominator) | shares	52,315,958	52,324,350
Per-share amount (in dollars per share) | $ / shares	$ 1.41	$ 1.13
Class B common stock
Reconciliation of the numerators and denominators used in the basic and diluted per-share computations
Ratio for converting shares of Class B common stock into shares of Class A common stock	2,400		2,400
Income available to stockholders (Basic EPS:)
Allocated net income (numerator) | $	$ 602	$ 486
Weighted shares (denominator) | shares	2,542	2,542
Per-share amount (in dollars per share) | $ / shares	$ 237	$ 191
Income available to stockholders on equivalent shares (Diluted EPS:)
Weighted shares (denominator) | shares	2,542	2,542
Per-share amount (in dollars per share) | $ / shares	$ 237	$ 191
Allocated net income (numerator) | $	$ 602	$ 486