Updates to Significant Accounting Policies - Impact On Financial Statements Narratives (Details) - USD ($) $ in Millions	6 Months Ended			12 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	[1]	Dec. 29, 2017	Dec. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities	$ 267.8	$ 253.4
Net cash used in investing activities	(384.8)	(110.4)
Net cash provided by financing activities	$ 337.6	$ 14.7
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities				$ 0.0	$ 0.0
Net cash used in investing activities				0.0	0.0
Net cash provided by financing activities				$ 0.0	$ 0.0

[1] See Note 2 for a summary of adjustments