Earnings per Share and Stock Repurchase Program (Details) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares	Sep. 27, 2020 USD ($) $ / shares	Jun. 28, 2020 USD ($) $ / shares	Mar. 29, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares	Sep. 29, 2019 USD ($) $ / shares	Jun. 30, 2019 USD ($) $ / shares	Mar. 31, 2019 USD ($) $ / shares	Dec. 31, 2020 USD ($) item $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Feb. 06, 2019 USD ($)	Jul. 27, 2015 USD ($)
Common Stock
Common Stock conversion ratio, at the option of the holder									1
Net (loss) income
Net income	$ 29.2	$ 32.9	$ 20.2	$ 32.0	$ 31.8	$ 32.3	$ 36.4	$ 31.0	$ 114.3	$ 131.5	$ 128.0
Shares
Shares (in shares) | shares									33,900,000	34,100,000	34,300,000
Per Share Amount
Net income (in dollars per share) | $ / shares	$ 0.86	$ 0.97	$ 0.60	$ 0.94	$ 0.94	$ 0.95	$ 1.06	$ 0.91	$ 3.37	$ 3.86	$ 3.73
Dilutive securities, principally common stock options
Common stock equivalents (in shares) | shares										100,000
Common stock equivalents (in dollars per share) | $ / shares									$ (0.01)	$ (0.01)
Net (loss) income
Net income									$ 114.3	$ 131.5	$ 128.0
Weighted average number of shares:
Shares (in shares) | shares									34,000,000.0	34,200,000	34,300,000
Securities not included in the computation of diluted EPS
Net income (in dollars per share) | $ / shares	$ 0.86	$ 0.97	$ 0.59	$ 0.94	$ 0.93	$ 0.94	$ 1.06	$ 0.91	$ 3.36	$ 3.85	$ 3.73
Shares repurchased
Number of repurchase plans | item									2
Cost of shares repurchased									$ 28.9	$ 19.5	$ 26.0
Class A
Common Stock
Common Stock, votes per share (Number of votes)	1				1				1	1
Shares of Common Stock reserved for issuance under stock-based compensation plans | shares	2,252,875								2,252,875
Shares repurchased
Number of shares repurchased | shares									331,531	227,620
Cost of shares repurchased									$ 28.9	$ 19.5
Class B
Common Stock
Common Stock, votes per share (Number of votes)	10				10				10	10
Shares of Common Stock reserved for conversion | shares	6,144,290								6,144,290
July 27, 2015 | Class A
Shares repurchased
Value of shares of the entity's Class A common stock authorized to be repurchased													$ 100.0
Number of shares repurchased | shares										146,304
Cost of shares repurchased										$ 11.8
February 6, 2019 | Class A
Shares repurchased
Value of shares of the entity's Class A common stock authorized to be repurchased												$ 150.0
Number of shares repurchased | shares									331,531	81,316
Cost of shares repurchased									$ 28.9	$ 7.7
Remaining authorized repurchase amount	$ 113.4								$ 113.4