Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income	$ 20.4	$ 31.1
Denominator:
Weighted-average shares used to compute basic net income per share (in shares)	330.8	348.1
Dilutive effect of employee stock awards (in shares)	4.3	4.6
Weighted-average shares used to compute diluted net income per share (in shares)	335.1	352.7
Net income per share
Basic (in dollars per share)	$ 0.06	$ 0.09
Diluted, (in dollars per share)	$ 0.06	$ 0.09
Anti-dilutive shares (in shares)	3.3	5.0