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Income Taxes - Schedule of Reconciliation of Beginning and Ending Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Unrecognized tax benefits at the beginning of year	$ 25.2	$ 24.2	$ 26.3
Gross increases - current year tax positions	0.6	0.7	0.6
Gross increases - prior year tax positions	2.4	0.7	5.4
Gross decreases - prior year tax positions	(3.3)	(0.4)	(8.1)
Unrecognized tax benefits at end of year	24.9	25.2	24.2
Interest and penalties in year-end balance	$ 1.5	$ (0.9)	$ 0.5

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- Definition

Unrecognized Tax Benefits Net Of Federal Benefits On State Income Tax Positions And Interest

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- Definition

Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)(1)
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Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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-Publisher FASB
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-Topic 740
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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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-Name Accounting Standards Codification
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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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