Leases - Lease Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 27, 2020	Dec. 29, 2019
Leases [Abstract]
Amortization of right of use assets - finance leases	$ 2.1	$ 2.0
Interest expense on lease liabilities - finance leases	2.6	2.5
Operating lease cost (expense resulting from amortization of total lease payments)	11.9	13.2
Short-term lease cost	0.8	0.6
Variable lease cost (cost excluded from lease payments)	0.1	0.1
Sublease income	(1.1)	(3.3)
Total lease cost	$ 16.4	$ 15.1