Earnings per Share and Stock Repurchase Program (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Jul. 31, 2023 USD ($)	Feb. 06, 2019 USD ($)
Common Stock
Common Stock conversion ratio, at the option of the holder	1
Net (loss) income
Net income | $	$ 262.1	$ 251.5	$ 165.7
Shares
Shares (in shares)	33,400,000	33,500,000	33,800,000
Per Share Amount
Net income (in dollars per share) | $ / shares	$ 7.85	$ 7.51	$ 4.90
Dilutive securities, principally common stock options
Common stock equivalents (in shares)	100,000	100,000	100,000
Common stock equivalents (in dollars per share) | $ / shares	$ (0.03)	$ (0.03)	$ (0.02)
Net (loss) income
Net income | $	$ 262.1	$ 251.5	$ 165.7
Weighted average number of shares:
Shares (in shares)	33,500,000	33,600,000	33,900,000
Securities not included in the computation of diluted EPS
Net income (in dollars per share) | $ / shares	$ 7.82	$ 7.48	$ 4.88
Shares repurchased
Number of shares repurchased	91,622	493,733	109,998
Stock Repurchased During Period, Value | $	$ 16.0	$ 69.4	$ 16.0
Class A
Common Stock
Common Stock, votes per share (Number of votes)	1	1
Shares of Common Stock reserved for issuance under stock-based compensation plans	1,967,652
Class B
Common Stock
Common Stock, votes per share (Number of votes)	10	10
Shares of Common Stock reserved for conversion	5,958,290
February 6, 2019 | Class A
Shares repurchased
Value of shares of the entity's Class A common stock authorized to be repurchased | $				$ 150.0	$ 150.0
Remaining authorized repurchase amount | $	$ 12.0