Segment Reporting - Revenues by Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Schedule Of Revenues From External Customers [Line Items]
Total	$ 599.2	$ 609.3	$ 603.6	$ 560.8	$ 571.3	$ 580.9	$ 580.6	$ 536.9	$ 2,372.9	$ 2,269.7	$ 1,623.2
United States
Schedule Of Revenues From External Customers [Line Items]
Total									1,786.9	1,709.0	1,299.0
United Kingdom
Schedule Of Revenues From External Customers [Line Items]
Total									173.2	160.0	130.3
Canada
Schedule Of Revenues From External Customers [Line Items]
Total									64.1	61.8	61.2
All other countries
Schedule Of Revenues From External Customers [Line Items]
Total									$ 348.7	$ 338.9	$ 132.7