Consolidated Statements of Stockholders Equity - USD ($) $ in Millions	Class A Common Stock	Class B Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss.	Total
Balance at the beginning of the period at Dec. 31, 2020	$ 2.8	$ 0.6	$ 606.3	$ 560.1	$ (100.0)	$ 1,069.8
Balance (in shares) at Dec. 31, 2020	27,478,512	6,144,290
Increase (Decrease) in Stockholders' Equity
Net income				165.7		165.7
Other comprehensive income (loss)					(27.3)	(27.3)
Comprehensive income						138.4
Shares of Class B common stock converted to Class A common stock (in shares)	120,000	(120,000)
Shares of Class A common stock issued upon the exercise of stock options			0.1			0.1
Shares of Class A common stock issued upon the exercise of stock options (in shares)	1,440
Stock-based compensation			22.9			22.9
Stock repurchase				(16.0)		(16.0)
Stock repurchase (in shares)	(109,998)
Net change in restricted stock units			1.9	(9.6)		(7.7)
Net change in restricted stock units (in shares)	94,571
Common stock dividends				(34.3)		(34.3)
Balance at the end of the period at Dec. 31, 2021	$ 2.8	$ 0.6	631.2	665.9	(127.3)	1,173.2
Balance (in shares) at Dec. 31, 2021	27,584,525	6,024,290
Increase (Decrease) in Stockholders' Equity
Net income				251.5		251.5
Other comprehensive income (loss)					(22.6)	(22.6)
Comprehensive income						228.9
Shares of Class B common stock converted to Class A common stock (in shares)	66,000	(66,000)
Shares of Class A common stock issued upon the exercise of stock options			0.2			0.2
Shares of Class A common stock issued upon the exercise of stock options (in shares)	2,325
Stock-based compensation			18.4			18.4
Stock repurchase	$ (0.1)			(69.3)		(69.4)
Stock repurchase (in shares)	(493,733)
Net change in restricted stock units			2.1	(13.3)		(11.2)
Net change in restricted stock units (in shares)	155,562
Common stock dividends				(39.5)		(39.5)
Balance at the end of the period at Dec. 31, 2022	$ 2.7	$ 0.6	651.9	795.3	(149.9)	1,300.6
Balance (in shares) at Dec. 31, 2022	27,314,679	5,958,290
Increase (Decrease) in Stockholders' Equity
Net income				262.1		262.1
Other comprehensive income (loss)					6.5	6.5
Comprehensive income						268.6
Shares of Class A common stock issued upon the exercise of stock options			0.1			0.1
Shares of Class A common stock issued upon the exercise of stock options (in shares)	598
Stock-based compensation			20.2			20.2
Stock repurchase				(16.0)		(16.0)
Stock repurchase (in shares)	(91,622)
Net change in restricted stock units			2.1	(15.8)		(13.7)
Net change in restricted stock units (in shares)	129,046
Common stock dividends				(46.5)		(46.5)
Balance at the end of the period at Dec. 31, 2023	$ 2.7	$ 0.6	$ 674.3	$ 979.1	$ (143.4)	$ 1,513.3
Balance (in shares) at Dec. 31, 2023	27,352,701	5,958,290