Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income	$ 61.2	$ 46.2	$ 81.6	$ 77.3
Denominator:
Weighted-average shares used to compute basic net income per share (in shares)	331.0	346.3	330.9	347.2
Dilutive effect of employee stock awards (in shares)	2.1	2.8	3.8	4.5
Weighted-average shares used to compute diluted net income per share (in shares)	333.1	349.1	334.7	351.7
Net income per share
Basic (in dollars per share)	$ 0.18	$ 0.13	$ 0.25	$ 0.22
Diluted, (in dollars per share)	$ 0.18	$ 0.13	$ 0.24	$ 0.22
Anti-dilutive shares (in shares)	7.6	6.8	6.1	7.0