Reclassifications from Accumulated Other Comprehensive (Loss) Income (AOCI) - Schedule of amounts reclassified from AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales	$ 342.8	$ 460.4	$ 692.6	$ 933.1
Net sales	348.8	573.0	702.1	1,158.4
Interest expense	7.9	5.3	14.6	10.7
(Loss) gain	1.3	0.8	(1.1)	0.5
(Loss) income before income taxes	(95.6)	50.5	(161.7)	104.6
Tax (expense)/benefit	10.7	(11.7)	29.7	(24.6)
Net (loss) income	(84.9)	38.8	(132.0)	80.0
Amount Reclassified from AOCI | Cash flow hedging items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
(Loss) income before income taxes	2.5	3.0	5.4	8.3
Tax (expense)/benefit	(0.5)	(0.7)	(1.3)	(2.0)
Net (loss) income	2.0	2.3	4.1	6.3
Amount Reclassified from AOCI | Pension and other postretirement benefit plan items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
(Loss) income before income taxes	(4.7)	(4.0)	(9.4)	(8.0)
Tax (expense)/benefit	1.1	1.0	2.2	2.0
Net (loss) income	(3.6)	(3.0)	(7.2)	(6.0)
Amount Reclassified from AOCI | Net actuarial loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
(Loss) gain	(5.2)	(4.5)	(10.4)	(9.0)
Amount Reclassified from AOCI | Prior service benefit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
(Loss) gain	0.5	0.5	1.0	1.0
Amount Reclassified from AOCI | Commodity contracts | Cash flow hedging items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales	2.4	2.8	5.2	7.5
Amount Reclassified from AOCI | Foreign exchange contracts | Cash flow hedging items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net sales	0.0	0.1	0.0	0.6
Amount Reclassified from AOCI | Forward interest rate swaps | Cash flow hedging items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 0.1	$ 0.1	$ 0.2	$ 0.2