Lease Commitments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Leases [Abstract]
Sublease income on operating leases	$ 7.4
Operating Leases
2018	18.0
2019	19.5
2020	14.3
2021	11.4
2022	9.3
Thereafter	55.3
Total future minimum lease payments	127.8
Gross rent expense under operating leases	21.5	$ 21.6	$ 23.1
Sublease income	3.4	3.3	3.3
Accrual for excess facilities
Accrual for excess facilities - beginning balance	4.0	5.5
Adjustment of excess facility accrual	0.0	0.0
Cash payments	(0.7)	(1.5)
Accrual for excess facilities - ending balance	3.3	4.0	$ 5.5
Deferred rent	$ 3.3	$ 3.9