Condensed Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
REVENUE:
Total revenue	$ 615.5	$ 521.7	$ 1,192.4	$ 994.3
COST OF REVENUE:
Total cost of revenue	135.1	128.3	263.8	241.3
GROSS PROFIT:
Total gross profit	480.4	393.4	928.6	753.0
OPERATING EXPENSES:
Research and development	82.1	67.4	162.4	136.0
Sales and marketing	253.8	226.5	513.8	442.4
General and administrative	28.9	24.3	57.7	48.8
Gain on intellectual property matter	(1.1)	0.0	(37.9)	0.0
Total operating expenses	363.7	318.2	696.0	627.2
OPERATING INCOME	116.7	75.2	232.6	125.8
INTEREST INCOME—NET	4.0	11.0	13.2	21.2
OTHER INCOME (EXPENSE)—NET	0.9	(0.4)	(7.1)	(0.9)
INCOME BEFORE INCOME TAXES	121.6	85.8	238.7	146.1
PROVISION FOR INCOME TAXES	9.5	13.1	22.6	14.6
NET INCOME	$ 112.1	$ 72.7	$ 216.1	$ 131.5
Net income per share (Note 8):
Basic (in dollars per share)	$ 0.69	$ 0.42	$ 1.30	$ 0.77
Diluted (in dollars per share)	$ 0.68	$ 0.42	$ 1.27	$ 0.75
Weighted-average shares outstanding:
Basic (in shares)	161.6	171.1	166.1	170.6
Diluted (in shares)	165.4	175.1	169.8	175.0
Product [Member]
REVENUE:
Total revenue	$ 211.9	$ 189.9	$ 404.2	$ 352.6
COST OF REVENUE:
Total cost of revenue	84.4	82.7	160.7	152.9
GROSS PROFIT:
Total gross profit	127.5	107.2	243.5	199.7
Service [Member]
REVENUE:
Total revenue	403.6	331.8	788.2	641.7
COST OF REVENUE:
Total cost of revenue	50.7	45.6	103.1	88.4
GROSS PROFIT:
Total gross profit	$ 352.9	$ 286.2	$ 685.1	$ 553.3