Segment Reporting - Revenues by Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Jan. 02, 2021	Sep. 26, 2020	Jun. 27, 2020	Mar. 28, 2020	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Schedule Of Revenues From External Customers [Line Items]
Total	$ 505.0	$ 517.5	$ 456.8	$ 474.2	$ 440.0	$ 472.1	$ 455.6	$ 427.7	$ 1,953.5	$ 1,795.4	$ 1,791.0
United States
Schedule Of Revenues From External Customers [Line Items]
Total									1,429.6	1,210.0	1,205.0
United Kingdom
Schedule Of Revenues From External Customers [Line Items]
Total									142.2	172.0	173.2
Canada
Schedule Of Revenues From External Customers [Line Items]
Total									64.1	67.0	64.1
All other countries
Schedule Of Revenues From External Customers [Line Items]
Total									$ 317.6	$ 346.4	$ 348.7