Earnings Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Earnings Per Share [Abstract]
Net earnings	$ 33.1	$ 23.0	$ 46.8	$ 53.9
Less: earnings allocated to participating securities	(0.4)	(0.3)	(0.5)	(0.9)
Net earnings available to common shareholders	$ 32.7	$ 22.7	$ 46.3	$ 53.0
Average shares outstanding (millions):
Basic (in shares)	38.8	38.3	38.7	38.3
Dilutive share awards (in shares)	0.1	0.5	0.1	0.5
Diluted (in shares)	38.9	38.8	38.8	38.8
Basic earnings per share on common stock (in dollars per share)	$ 0.84	$ 0.59	$ 1.20	$ 1.38
Diluted earnings per share on common stock (in dollars per share)	$ 0.84	$ 0.58	$ 1.19	$ 1.37