Deferred Revenue And Performance Obligations - Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 30, 2018	Mar. 31, 2017	[1]
Revenue Recognition and Deferred Revenue [Abstract]
Balance as of prior fiscal year end	$ 276.6	$ 246.4
Revenue recognized from prior fiscal year end	(98.0)	(87.8)
Acquired deferred revenue	22.3	4.0
Net deferred revenue activity	159.5	139.9
Balance as of the end of the first quarter	$ 360.4	$ 302.5

[1] See Note 2 for a summary of adjustments