Reclassifications from Accumulated Other Comprehensive (Loss) Income (AOCI) - Schedule of changes in AOCI by component, net of tax (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances, period start	$ 1,577.0	$ 1,490.7	$ 1,520.1	$ 1,485.9
Cumulative adjustment upon adoption of ASU 2017-12	0.0	0.0	0.0	(1.0)
Other comprehensive (loss) income before reclassifications	(9.4)	(17.6)	15.8	(40.8)
Amounts reclassified from AOCI	0.7	1.2	(0.3)	4.1
Other comprehensive (loss) income, net of tax	(8.7)	(16.4)	15.5	(37.7)
Balances, period end	1,603.4	1,505.5	1,603.4	1,505.5
Cash flow hedging items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances, period start	11.9	(0.2)	(14.8)	23.8
Cumulative adjustment upon adoption of ASU 2017-12				(1.0)
Other comprehensive (loss) income before reclassifications	(16.8)	(14.9)	13.9	(39.1)
Amounts reclassified from AOCI	(2.3)	(0.5)	(6.3)	0.7
Other comprehensive (loss) income, net of tax	(19.1)	(15.4)	7.6	(39.4)
Balances, period end	(7.2)	(15.6)	(7.2)	(15.6)
Pension and other postretirement benefit plan items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances, period start	(290.3)	(218.7)	(293.3)	(220.4)
Cumulative adjustment upon adoption of ASU 2017-12				0.0
Other comprehensive (loss) income before reclassifications	0.0	0.0	0.0	0.0
Amounts reclassified from AOCI	3.0	1.7	6.0	3.4
Other comprehensive (loss) income, net of tax	3.0	1.7	6.0	3.4
Balances, period end	(287.3)	(217.0)	(287.3)	(217.0)
Unrealized gains (losses) on available-for-sale securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances, period start	0.0	0.0	0.0	(0.3)
Cumulative adjustment upon adoption of ASU 2017-12				0.0
Other comprehensive (loss) income before reclassifications	0.0	0.0	0.0	0.3
Amounts reclassified from AOCI	0.0	0.0	0.0	0.0
Other comprehensive (loss) income, net of tax	0.0	0.0	0.0	0.3
Balances, period end	0.0	0.0	0.0	0.0
Foreign currency items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances, period start	(49.2)	(42.2)	(43.7)	(42.9)
Cumulative adjustment upon adoption of ASU 2017-12				0.0
Other comprehensive (loss) income before reclassifications	7.4	(2.7)	1.9	(2.0)
Amounts reclassified from AOCI	0.0	0.0	0.0	0.0
Other comprehensive (loss) income, net of tax	7.4	(2.7)	1.9	(2.0)
Balances, period end	(41.8)	(44.9)	(41.8)	(44.9)
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances, period start	(327.6)	(261.1)	(351.8)	(239.8)
Balances, period end	$ (336.3)	$ (277.5)	$ (336.3)	$ (277.5)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Represents the quantification of the effect of adopting the new accounting standard or change in accounting principle expected by the entity to have a significant effect on the entity's financial statements.

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- Definition

Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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