Leases - Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Leases [Abstract]
Amortization of right of use assets - finance leases	$ 0.6	$ 0.5	$ 1.6	$ 1.5
Interest on lease liabilities - finance leases	0.6	0.6	1.9	1.9
Operating lease cost	2.7	3.6	9.1	10.2
Short-term lease cost	0.2	0.1	0.6	0.5
Variable lease cost (cost excluded from lease payments)	0.0	0.0	0.1	0.1
Sublease income	(0.1)	(0.8)	(1.1)	(2.4)
Total lease cost	$ 4.0	$ 4.0	$ 12.2	$ 11.8