Cash and Cash Equivalents, Available for Sale Investments (Details) - USD ($) $ in Millions		Dec. 29, 2017	Dec. 30, 2016
Cash and Cash Equivalents [Line Items]
Available-for-sale Securities, Debt Securities		$ 205.7	$ 133.3
Cash and cash equivalents		26.8	22.2
Short-term investments		178.9	111.1
Total		205.7	133.3
US Treasury Securities [Member]
Cash and Cash Equivalents [Line Items]
Available-for-sale Securities, Debt Securities	[1]	9.6	11.7
Municipal Bonds [Member]
Cash and Cash Equivalents [Line Items]
Available-for-sale Securities, Debt Securities	[1]	0.0	10.0
Corporate Debt Securities [Member]
Cash and Cash Equivalents [Line Items]
Available-for-sale Securities, Debt Securities	[1]	96.0	31.7
Bank Time Deposits [Member]
Cash and Cash Equivalents [Line Items]
Available-for-sale Securities, Debt Securities	[1]	0.0	2.4
Commercial Paper [Member]
Cash and Cash Equivalents [Line Items]
Available-for-sale Securities, Debt Securities	[1]	$ 100.1	$ 77.5

[1] 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.