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Fair Value Measurements - Schedule of Fair Value of Financial Assets and Liabilities (Detail) - USD ($) $ in Millions | Mar. 31, 2018 | Jun. 30, 2017
--- | --- | ---
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets and liability |  | $ 100.6 | $ (24.8)
Money Market Funds [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets | [1] | 4.3 | 7.4
Corporate Bonds and Notes [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets |  | 61.6 | 50.4
Municipal Bonds [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets |  | 31.0 | 36.9
Federal Agency Issues [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets |  | 12.5 | 13.8
US Government Securities [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets |  | 8.2 | 7.2
Contingent Consideration [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial liability |  | (17.0) | (140.5)
Level 1 [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets and liability |  | 6.3 | 7.4
Level 1 [Member] | Money Market Funds [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets | [1] | 4.3 | 7.4
Level 1 [Member] | Corporate Bonds and Notes [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets |  | 2.0 |
Level 2 [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets and liability |  | 111.3 | 108.3
Level 2 [Member] | Corporate Bonds and Notes [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets |  | 59.6 | 50.4
Level 2 [Member] | Municipal Bonds [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets |  | 31.0 | 36.9
Level 2 [Member] | Federal Agency Issues [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets |  | 12.5 | 13.8
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 | 7.2
Level 3 [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial assets and liability |  | (17.0) | (140.5)
Level 3 [Member] | Contingent Consideration [Member] |  |  |
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] |  |  |
Total fair value of financial liability |  | $ (17.0) | $ (140.5)
[1] | Money market funds are primarily comprised of exchange traded funds and accrued interest

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