Pension and Other Postretirement Benefits - Schedule of components of the net periodic pension (income) expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2.1	$ 2.4	$ 4.2	$ 4.8
Interest cost	9.1	9.9	18.2	19.8
Expected return on plan assets	(14.9)	(13.9)	(29.8)	(27.8)
Amortization of net loss (gain)	2.1	4.3	4.2	8.6
Amortization of prior service cost (credits)	0.6	0.5	1.2	1.0
Net pension (income) expense	(1.0)	3.2	(2.0)	6.4
Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.6	0.6	1.3	1.4
Interest cost	1.8	1.9	3.5	3.8
Expected return on plan assets	(2.0)	(1.6)	(4.0)	(3.3)
Amortization of net loss (gain)	(0.2)	0.9	(0.4)	1.8
Amortization of prior service cost (credits)	(1.0)	(1.0)	(2.0)	(2.0)
Net pension (income) expense	$ (0.8)	$ 0.8	$ (1.6)	$ 1.7