Share-Based Compensation - Schedule of Shares Purchased and Compensation Expenses (Detail) - USD ($) shares in Millions, $ in Millions	12 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares purchased under the plans	0.1	0.5	0.2
Plan compensation expense	$ 0.1	$ 2.3	$ 1.9

The number of shares purchased on the open market during the period for issuance to employees under the plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5047-113901

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration