Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Oct. 01, 2017	Oct. 02, 2016	Jul. 27, 2015
Net (loss) income
Net income	$ 26.5	$ 21.9	$ 75.4	$ 66.7
Shares
Shares (in shares)	34,400,000	34,500,000	34,400,000	34,500,000
Per Share Amount
Net income (in dollars per share)	$ 0.77	$ 0.63	$ 2.19	$ 1.93
Dilutive securities, principally common stock options
Common stock equivalents (in shares)			100,000
Net (loss) income
Net income	$ 26.5	$ 21.9	$ 75.4	$ 66.7
Weighted average number of shares:
Shares (in shares)	34,400,000	34,500,000	34,500,000	34,500,000
Securities not included in the computation of diluted EPS
Net income (in dollars per share)	$ 0.77	$ 0.63	$ 2.19	$ 1.93
Shares repurchased
Options to purchase shares of Class A common stock	100,000		100,000
Number of shares repurchased			214,455	433,429
Cost of shares repurchased			$ 13.6	$ 22.2
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	$ 42.4		$ 42.4
July 27, 2015 | Class A
Shares repurchased
Number of shares repurchased		74,038	72,669
Cost of shares repurchased		$ 4.6	$ 4.7