Cash and Cash Equivalents, Available for Sale Investments (Details) - USD ($) $ in Millions		Dec. 28, 2018	Dec. 29, 2017
Cash and Cash Equivalents [Line Items]
Debt Securities, Available-for-sale		$ 0.0	$ 205.7
Cash and cash equivalents			26.8
Short-term investments		0.0	178.9	[1]
Total			205.7
US Treasury Securities [Member]
Cash and Cash Equivalents [Line Items]
Debt Securities, Available-for-sale	[2]	0.0	9.6
Corporate Debt Securities [Member]
Cash and Cash Equivalents [Line Items]
Debt Securities, Available-for-sale	[2]	0.0	96.0
Commercial Paper [Member]
Cash and Cash Equivalents [Line Items]
Debt Securities, Available-for-sale	[2]	$ 0.0	$ 100.1

[1] See Note 2 for a summary of adjustments

[2] The Company’s available-for sale securities are valued using readily available pricing sources for comparable instruments, or model-driven valuations using significant inputs derived from or corroborated by observable market data, including yield curves and credit ratings.