Earnings per Share and Stock Repurchase Program (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017	Jul. 27, 2015
Net (loss) income
Net income	$ 31.5	$ 26.5	$ 95.7	$ 75.4
Shares
Shares (in shares)	34,300,000	34,400,000	34,300,000	34,400,000
Per Share Amount
Net income (in dollars per share)	$ 0.92	$ 0.77	$ 2.79	$ 2.19
Dilutive securities, principally common stock options
Common stock equivalents (in shares)	100,000		100,000	100,000
Common stock equivalents (in dollars per share)			$ (0.01)
Net (loss) income
Net income	$ 31.5	$ 26.5	$ 95.7	$ 75.4
Weighted average number of shares:
Shares (in shares)	34,400,000	34,400,000	34,400,000	34,500,000
Securities not included in the computation of diluted EPS
Net income (in dollars per share)	$ 0.92	$ 0.77	$ 2.78	$ 2.19
Dilutive securities, principally common stock options
Options to purchase shares of Class A common stock, anti-dilutive	0	100,000	0	100,000
Shares repurchased
Number of shares repurchased	57,156	72,669	195,790	214,455
Cost of shares repurchased	$ 4.7	$ 4.7	$ 15.5	$ 13.6
Class A
Shares repurchased
Total value of shares of the entity's Class A common stock authorized to be repurchased					$ 100.0
Remaining authorized repurchase amount	$ 22.3		$ 22.3