Immaterial Correction of Prior Period Financial Statements - Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
ASSETS
DEFERRED TAX ASSETS	$ 230.1		$ 226.3
TOTAL ASSETS	3,586.2		3,879.2
CURRENT LIABILITIES:
Deferred revenue	1,300.0		1,155.8
Total current liabilities	1,645.6		1,455.8
DEFERRED REVENUE	1,092.0		953.3
Total liabilities	2,873.0		2,536.8
Retained earnings (accumulated deficit)	(466.9)		160.8
Total stockholders’ equity	713.2	$ 566.7	1,342.4	$ 1,217.9	$ 1,139.4	$ 1,025.5
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 3,586.2		3,879.2
As Previously Reported [Member]
ASSETS
DEFERRED TAX ASSETS			232.6
TOTAL ASSETS			3,885.5
CURRENT LIABILITIES:
Deferred revenue			1,173.6
Total current liabilities			1,473.6
DEFERRED REVENUE			962.3
Total liabilities			2,563.6
Retained earnings (accumulated deficit)			140.3
Total stockholders’ equity			1,321.9
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY			3,885.5
Corrections [Member]
ASSETS
DEFERRED TAX ASSETS			(6.3)
TOTAL ASSETS			(6.3)
CURRENT LIABILITIES:
Deferred revenue			(17.8)
Total current liabilities			(17.8)
DEFERRED REVENUE			(9.0)
Total liabilities			(26.8)
Retained earnings (accumulated deficit)			20.5
Total stockholders’ equity			20.5
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY			$ (6.3)