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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, 2020	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Unrecognized tax benefits at the beginning of year	$ 21.7	$ 24.9	$ 25.2
Gross increases - current year tax positions	1.6	2.2	0.6
Gross increases - prior year tax positions	0.7	0.5	2.4
Gross increases - acquisitions		2.3
Gross decreases - prior year tax positions		(0.1)	(3.3)
Gross decreases - settlements		(2.7)
Gross decreases - statute lapse	(0.5)	(5.4)
Unrecognized tax benefits at end of year	23.5	21.7	24.9
Interest and penalties in year-end balance	$ 1.4	$ 0.8	$ 1.5

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

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)(1)
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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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-Publisher FASB
-Name Accounting Standards Codification
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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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of increase in unrecognized tax benefits resulting from acquisitions.

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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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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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-Name Accounting Standards Codification
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-SubTopic 10
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