CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss)/Income	Accumulated Deficit	Total
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
Stock-based compensation		51.6			51.6
Stock-based compensation, shares	1,387,147
Foreign currency translation adjustment			(22.4)		(22.4)
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			2.5		2.5
Net income				52.3	52.3
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
Balance at Sep. 30, 2018	$ 0.2	1,907.7	(9.2)	(343.9)	1,554.8
Balance, shares at Sep. 30, 2018	247,132,693
Stock-based compensation		25.3			25.3
Stock-based compensation, shares	686,708
Foreign currency translation adjustment			(30.6)		(30.6)
Repurchase and retirement of common shares		(402.3)			(402.3)
Repurchase and retirement of common shares (in shares)	(12,967,663)
Defined benefit pension plan adjustments			4.4		4.4
Net income				30.2	30.2
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
Balance at Jun. 30, 2019	$ 0.2	1,581.2	(23.9)	(216.0)	$ 1,341.5
Balance, shares at Jun. 30, 2019	236,257,893				236,257,893
Stock-based compensation		51.2			$ 51.2
Stock-based compensation, shares	1,353,980
Foreign currency translation adjustment			3.3		3.3
Defined benefit pension plan adjustments			0.4		0.4
Net income				79.3	79.3
Balance at Dec. 31, 2019	$ 0.2	1,632.4	(20.2)	(136.7)	$ 1,475.7
Balance, shares at Dec. 31, 2019	237,611,873				237,611,873
Balance at Sep. 30, 2019	$ 0.2	1,607.5	(38.3)	(198.1)	$ 1,371.3
Balance, shares at Sep. 30, 2019	236,829,304
Stock-based compensation		24.9			24.9
Stock-based compensation, shares	782,569
Foreign currency translation adjustment			18.1		18.1
Net income				61.4	61.4
Balance at Dec. 31, 2019	$ 0.2	$ 1,632.4	$ (20.2)	$ (136.7)	$ 1,475.7
Balance, shares at Dec. 31, 2019	237,611,873				237,611,873