CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 1.5	$ 167.0	$ 188.5
Other comprehensive (loss) income, net of tax
Cumulative adjustment upon adoption of ASU 2017-12 reclassified to reinvested earnings	0.0	(1.0)	0.0
Pension and postretirement (losses) benefits, net of tax of $13.2, $23.2 and $(26.3), respectively	(41.0)	(72.9)	78.6
Net gain (loss) on derivative instruments, net of tax of $(1.2), $13.3 and $(13.7), respectively	3.7	(37.6)	26.1
Marketable securities gain, net of tax of $0.0, $0.0 and $0.0, respectively	0.0	0.3	0.0
Foreign currency translation	(8.9)	(0.8)	(1.4)
Other comprehensive (loss) income, net of tax	(46.2)	(112.0)	103.3
Comprehensive (loss) income, net of tax	$ (44.7)	$ 55.0	$ 291.8