CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Common Stock	Additional paid-in Capital	Accumulated Other Comprehensive Income/(Loss)	Accumulated Deficit	Total
Balance at Jun. 30, 2017	$ 0.2	$ 1,884.0	$ 5.4	$ (468.9)	$ 1,420.7
Balance, shares at Jun. 30, 2017	246,471,551
Stock-based compensation		67.8			67.8
Stock-based compensation, shares	2,192,075
Foreign currency translation adjustment, net of tax			14.8		14.8
Defined benefit pension plan adjustments, net of tax			(10.8)		(10.8)
Net income				60.0	60.0
Balance at Mar. 31, 2018	$ 0.2	1,951.8	9.4	(408.9)	1,552.5
Balance, shares at Mar. 31, 2018	248,663,626
Balance at Jun. 30, 2017	$ 0.2	1,884.0	5.4	(468.9)	1,420.7
Balance, shares at Jun. 30, 2017	246,471,551
Balance at Jun. 30, 2018	$ 0.2	1,881.6	(15.5)	(366.0)	$ 1,500.3
Balance, shares at Jun. 30, 2018	246,438,483				246,438,483
Balance at Dec. 31, 2017	$ 0.2	1,931.2	23.3	(432.4)	$ 1,522.3
Balance, shares at Dec. 31, 2017	248,105,766
Stock-based compensation		20.6			20.6
Stock-based compensation, shares	557,860
Foreign currency translation adjustment, net of tax			(8.1)		(8.1)
Defined benefit pension plan adjustments, net of tax			(5.8)		(5.8)
Net income				23.5	23.5
Balance at Mar. 31, 2018	$ 0.2	1,951.8	9.4	(408.9)	1,552.5
Balance, shares at Mar. 31, 2018	248,663,626
Balance at Jun. 30, 2018	$ 0.2	1,881.6	(15.5)	(366.0)	$ 1,500.3
Balance, shares at Jun. 30, 2018	246,438,483				246,438,483
Stock-based compensation		74.9			$ 74.9
Stock-based compensation, shares	2,119,173
Foreign currency translation adjustment, net of tax			(15.2)		(15.2)
Repurchase and retirement of common shares		(402.5)			(402.5)
Repurchase and retirement of common shares (in shares)	(12,973,892)
Defined benefit pension plan adjustments, net of tax			2.4		2.4
Net income				87.0	87.0
Balance at Mar. 31, 2019	$ 0.2	1,554.0	(28.3)	(279.0)	$ 1,246.9
Balance, shares at Mar. 31, 2019	235,583,764				235,583,764
Balance at Dec. 31, 2018	$ 0.2	1,530.7	(35.4)	(313.7)	$ 1,181.8
Balance, shares at Dec. 31, 2018	234,851,738
Stock-based compensation		23.3			23.3
Stock-based compensation, shares	732,026
Foreign currency translation adjustment, net of tax			7.2		7.2
Defined benefit pension plan adjustments, net of tax			(0.1)		(0.1)
Net income				34.7	34.7
Balance at Mar. 31, 2019	$ 0.2	$ 1,554.0	$ (28.3)	$ (279.0)	$ 1,246.9
Balance, shares at Mar. 31, 2019	235,583,764				235,583,764