Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Class A common stock
Income available to stockholders (Basic EPS:)
Allocated net income (numerator) (in dollars)	$ 58,840	$ 74,694
Weighted shares (denominator) (in shares)	46,188,789	46,188,337
Per-share amount (in dollars per share)	$ 1.27	$ 1.62
Dilutive effect of stock-based awards
Allocated net income (numerator) (in dollars)	$ 0	$ 0
Weighted shares (denominator) (in shares)	34,761	22,899
Assumed conversion of Class B shares
Allocated net income (numerator) (in dollars)	$ 486	$ 617
Weighted shares (denominator) (in shares)	6,100,800	6,100,800
Income available to stockholders on equivalent shares (Diluted EPS:)
Allocated net income (numerator) (in dollars)	$ 59,326	$ 75,311
Weighted shares (denominator) (in shares)	52,324,350	52,312,036
Per-share amount (in dollars per share)	$ 1.13	$ 1.44
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 (as a percent)	2400.00%		2400.00%
Income available to stockholders (Basic EPS:)
Allocated net income (numerator) (in dollars)	$ 486	$ 617
Weighted shares (denominator) (in shares)	2,542	2,542
Income available to stockholders on equivalent shares (Diluted EPS:)
Allocated net income (numerator) (in dollars)	$ 486	$ 617
Weighted shares (denominator) (in shares)	2,542	2,542
Class B – Basic and diluted EPS:
Weighted shares (denominator) (in shares)	2,542	2,542
Per share amount (in dollars per share)	$ 191	$ 243