Reclassifications from Accumulated Other Comprehensive Income (Loss) (AOCI) - Schedule of changes in AOCI by component, net of tax (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Changes in the balance of Accumulated Other Comprehensive Income
Balances, period start			$ 1,198.6	$ 1,104.9
Balances, period end	$ 1,371.1	$ 1,161.6	1,371.1	1,161.6
Cash flow hedging items
Changes in the balance of Accumulated Other Comprehensive Income
Balances, period start	20.8	(7.2)	(2.3)	(21.8)
Other comprehensive income (loss) before reclassifications	2.6	5.5	23.7	9.4
Amounts reclassified from AOCI	(1.3)	1.7	0.7	12.4
Net current-period other comprehensive income (loss)	1.3	7.2	24.4	21.8
Balances, period end	22.1	0.0	22.1	0.0
Pension and other postretirement benefit plan items
Changes in the balance of Accumulated Other Comprehensive Income
Balances, period start	(294.4)	(321.2)	(299.0)	(344.3)
Other comprehensive income (loss) before reclassifications	0.0	0.0	0.0	11.7
Amounts reclassified from AOCI	2.1	5.7	6.7	17.1
Net current-period other comprehensive income (loss)	2.1	5.7	6.7	28.8
Balances, period end	(292.3)	(315.5)	(292.3)	(315.5)
Unrealized losses on available-for- sale securities
Changes in the balance of Accumulated Other Comprehensive Income
Balances, period start	(0.3)	(0.3)	(0.3)	(0.3)
Other comprehensive income (loss) before reclassifications	0.0	0.0	0.0	0.0
Amounts reclassified from AOCI	0.0	0.0	0.0	0.0
Net current-period other comprehensive income (loss)	0.0	0.0	0.0	0.0
Balances, period end	(0.3)	(0.3)	(0.3)	(0.3)
Foreign currency items
Changes in the balance of Accumulated Other Comprehensive Income
Balances, period start	(41.2)	(48.2)	(41.5)	(43.5)
Other comprehensive income (loss) before reclassifications	3.7	2.6	4.0	(2.1)
Amounts reclassified from AOCI	0.0	0.0	0.0	0.0
Net current-period other comprehensive income (loss)	3.7	2.6	4.0	(2.1)
Balances, period end	(37.5)	(45.6)	(37.5)	(45.6)
Accumulated Other Comprehensive (Loss) Income
Changes in the balance of Accumulated Other Comprehensive Income
Balances, period start	(315.1)	(376.9)	(343.1)	(409.9)
Other comprehensive income (loss) before reclassifications	6.3	8.1	27.7	19.0
Amounts reclassified from AOCI	0.8	7.4	7.4	29.5
Net current-period other comprehensive income (loss)	7.1	15.5	35.1	48.5
Balances, period end	$ (308.0)	$ (361.4)	$ (308.0)	$ (361.4)