Fair Value Measurements - Schedule of Fair Value of Financial Assets and Liabilities (Detail) - USD ($) $ in Millions		Dec. 31, 2018	Jun. 30, 2018
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets and liability		$ 105.4	$ 101.2
Money Market Funds [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets	[1]	16.4	12.5
Corporate Bonds and Notes [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		68.4	53.3
Municipal Bonds [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		17.0	29.2
Federal Agency Issues [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		12.0	12.4
US Government Securities [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		7.3	8.3
Contingent Consideration [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial liability		(15.7)	(14.5)
Level 1 [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets and liability		16.4	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]	16.4	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			2.8
Level 2 [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets and liability		104.7	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		68.4	50.5
Level 2 [Member] | Municipal Bonds [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets		17.0	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		12.0	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		7.3	8.3
Level 3 [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial assets and liability		(15.7)	(14.5)
Level 3 [Member] | Contingent Consideration [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Total fair value of financial liability		$ (15.7)	$ (14.5)

[1] Money market funds are primarily comprised of exchange traded funds and accrued interest