RECENT ACCOUNTING PRONOUNCEMENTS Adoption of ASU 2017-07 - Restatement of Prior Year Amounts (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs of revenue	$ 470.8	$ 425.9		$ 935.9	$ 848.6
General and administrative expenses	63.0	64.6		128.1	130.3
Sales and marketing expenses	43.4	43.8		86.9	86.9
Research and development expenses	25.8	22.6		50.5	45.0
Operating income	80.3	59.1	[1]	190.9	116.1	[1]
Interest and non-operating (income) expenses, net	$ 1.5	0.5		$ 3.3	2.7
Accounting Standards Update 2017-07 [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs of revenue		(0.6)			(1.4)
General and administrative expenses		(0.7)			(1.2)
Sales and marketing expenses		(0.1)			(0.1)
Research and development expenses					(0.1)
Operating income		1.4			2.8
Interest and non-operating (income) expenses, net		1.4			2.8
Accounting Standards Update 2017-07 [Member] | Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs of revenue		426.5			850.0
General and administrative expenses		65.3			131.5
Sales and marketing expenses		43.9			87.0
Research and development expenses					45.1
Operating income		57.7			113.3
Interest and non-operating (income) expenses, net		$ (0.9)			$ (0.1)

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