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Fair Value Measurements - Schedule of Fair Value of Financial Assets and Liabilities (Detail) - USD ($) $ in Millions		Sep. 30, 2018	Jun. 30, 2018
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets and liability		$ 93.0	$ 101.2
Money Market Funds [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets	[1]	6.1	12.5
Corporate Bonds and Notes [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		60.7	53.3
Municipal Bonds [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		23.4	29.2
Federal Agency Issues [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		9.5	12.4
US Government Securities [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		8.2	8.3
Contingent Consideration [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial liability		(14.9)	(14.5)
Level 1 [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets and liability		9.5	15.3
Level 1 [Member] | Money Market Funds [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets	[1]	6.1	12.5
Level 1 [Member] | Corporate Bonds and Notes [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		3.4	2.8
Level 2 [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets and liability		98.4	100.4
Level 2 [Member] | Corporate Bonds and Notes [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		57.3	50.5
Level 2 [Member] | Municipal Bonds [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		23.4	29.2
Level 2 [Member] | Federal Agency Issues [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		9.5	12.4
Level 2 [Member] | US Government Securities [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		8.2	8.3
Level 3 [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets and liability		(14.9)	(14.5)
Level 3 [Member] | Contingent Consideration [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial liability		$ (14.9)	$ (14.5)
[1] Money market funds are primarily comprised of exchange traded funds and accrued interest

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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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