Changes in Accumulated Other Comprehensive Income/(Loss) by Component Changes in Accumulated Other Comprehensive Income/(Loss) by Component - Summary of Components of AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	$ 1,127.5	$ 1,094.3	$ 1,003.8
Cumulative effect of changes in accounting principle	1,346.5	1,094.3	1,094.3
Other comprehensive income/(loss) before reclassifications	(30.7)	(18.7)	6.7
Amounts reclassified from accumulated other comprehensive income/(loss)	1.5	0.9	(2.7)
Balance	1,346.5	1,127.5	1,094.3
Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	0.2	101.3
Cumulative effect of changes in accounting principle	0.2	101.3	101.3
Balance		0.2	101.3
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	(58.3)	(43.2)	(48.9)
Cumulative effect of changes in accounting principle	(84.7)	(58.3)	(43.2)
Other comprehensive income/(loss) before reclassifications	(26.4)	(15.0)	5.7
Amounts reclassified from accumulated other comprehensive income/(loss)	0.0	0.0	0.0
Balance	(84.7)	(58.3)	(43.2)
Foreign Currency Translation | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance		0.0
Cumulative effect of changes in accounting principle		0.0	0.0
Balance			0.0
Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	0.0	(0.4)	2.3
Cumulative effect of changes in accounting principle	0.0	0.0	(0.4)
Other comprehensive income/(loss) before reclassifications	0.0	0.0	1.1
Amounts reclassified from accumulated other comprehensive income/(loss)	0.0	0.0	(3.7)
Balance	0.0	0.0	(0.4)
Securities | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance		0.4
Cumulative effect of changes in accounting principle		0.4	0.4
Balance			0.4
Pension and Post- Retirement Liabilities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	(12.9)	(8.3)	(9.2)
Cumulative effect of changes in accounting principle	(15.7)	(12.9)	(8.3)
Other comprehensive income/(loss) before reclassifications	(4.2)	(3.6)	(0.1)
Amounts reclassified from accumulated other comprehensive income/(loss)	1.5	0.9	1.0
Balance	(15.7)	(12.9)	(8.3)
Pension and Post- Retirement Liabilities | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance		(1.9)
Cumulative effect of changes in accounting principle		(1.9)	(1.9)
Balance			(1.9)
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	(71.2)	(51.9)	(55.8)
Cumulative effect of changes in accounting principle	(100.4)	(71.2)	(51.9)
Balance	$ (100.4)	(71.2)	(51.9)
AOCI Attributable to Parent | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance		(1.5)
Cumulative effect of changes in accounting principle		$ (1.5)	(1.5)
Balance			$ (1.5)