Condensed Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
REVENUE:
Total revenue	$ 651.1	$ 548.1	$ 1,846.4	$ 1,544.9
COST OF REVENUE:
Total cost of revenue	139.2	124.1	403.0	365.4
GROSS PROFIT:
Total gross profit	511.9	424.0	1,443.4	1,179.5
OPERATING EXPENSES:
Research and development	90.0	69.9	252.4	205.9
Sales and marketing	266.7	227.4	780.5	669.8
General and administrative	29.4	26.1	87.1	74.9
Gain on intellectual property matter	(1.1)	0.0	(39.0)	0.0
Total operating expenses	385.0	323.4	1,081.0	950.6
OPERATING INCOME	126.9	100.6	362.4	228.9
INTEREST INCOME—NET	2.5	11.4	15.7	32.6
OTHER EXPENSE—NET	(1.0)	(6.0)	(8.1)	(6.9)
INCOME BEFORE INCOME TAXES	128.4	106.0	370.0	254.6
PROVISION FOR INCOME TAXES	5.0	25.8	28.2	41.1
NET INCOME	$ 123.4	$ 80.2	$ 341.8	$ 213.5
Net income per share (Note 10):
Basic (in dollars per share)	$ 0.76	$ 0.47	$ 2.07	$ 1.25
Diluted (in dollars per share)	$ 0.75	$ 0.46	$ 2.03	$ 1.22
Weighted-average shares outstanding:
Basic (in shares)	162.1	171.3	164.8	170.9
Diluted (in shares)	165.6	174.8	168.4	174.9
Product [Member]
REVENUE:
Total revenue	$ 223.8	$ 197.1	$ 628.0	$ 549.7
COST OF REVENUE:
Total cost of revenue	84.3	79.0	245.0	231.9
GROSS PROFIT:
Total gross profit	139.5	118.1	383.0	317.8
Service [Member]
REVENUE:
Total revenue	427.3	351.0	1,218.4	995.2
COST OF REVENUE:
Total cost of revenue	54.9	45.1	158.0	133.5
GROSS PROFIT:
Total gross profit	$ 372.4	$ 305.9	$ 1,060.4	$ 861.7