RECENT ACCOUNTING PRONOUNCEMENTS Adoption of ASU 2017-07 - Restatement of Prior Year Amounts (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs of revenue		$ 454.1	$ 441.2		$ 1,390.0	$ 1,289.8
General and administrative expenses		68.0	70.1		196.6	200.4
Sales and marketing expenses		40.8	41.3		127.7	128.2
Research and development expenses		24.2	23.0		74.7	68.0
Operating income		137.8	133.1	[1]	328.7	249.2	[1]
Interest and non-operating expenses, net		$ 0.7	5.5		$ 4.0	8.2
Accounting Standards Update 2017-07 [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs of revenue			(0.7)			(2.1)
General and administrative expenses			(4.5)			(5.7)
Sales and marketing expenses						(0.1)
Research and development expenses			(0.1)			(0.2)
Operating income			5.3			8.1
Interest and non-operating expenses, net			5.3			8.1
Accounting Standards Update 2017-07 [Member] | Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs of revenue			441.9			1,291.9
General and administrative expenses	[2]		74.6			206.1
Sales and marketing expenses						128.3
Research and development expenses			23.1			68.2
Operating income			127.8			241.1
Interest and non-operating expenses, net			$ 0.2			$ 0.1

[1] (a)Operating income and operating margin for the three and nine months ended September 30, 2017 has been restated to reflect the adoption of ASU 2017-07. Refer to Note 2, Recent Accounting Pronouncements for further information.

[2] (a)Previously reported General and administrative expenses excludes $0.9 in both the three and nine months ended September 30, 2017 related to gains on the sale of long-lived assets which has been reclassed to conform with current year presentation.