Segment Reporting - Revenues by Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Schedule Of Revenues From External Customers [Line Items]
Total	$ 600.2	$ 616.1	$ 604.1	$ 574.1	$ 599.2	$ 609.3	$ 603.6	$ 560.8	$ 2,394.5	$ 2,372.9	$ 2,269.7
U.S.
Schedule Of Revenues From External Customers [Line Items]
Total									1,801.7	1,786.9	1,709.0
United Kingdom
Schedule Of Revenues From External Customers [Line Items]
Total									172.0	173.2	160.0
Canada
Schedule Of Revenues From External Customers [Line Items]
Total									67.4	64.1	61.8
All other countries
Schedule Of Revenues From External Customers [Line Items]
Total									$ 353.4	$ 348.7	$ 338.9