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Organization and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2015
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Total costs and expenses | $ 185.0 | $ 176.5 | $ 189.6 | $ 102.8 | $ 180.7 | $ 189.2 | $ 179.5 | $ 171.8 | $ 653.9 | $ 721.2 | $ 587.1 | $ 588.9
Operating income (loss) | 15.9 | 14.6 | 3.1 | 85.1 | 18.9 | 5.5 | 17.2 | 7.1 | 118.7 | 48.7 | 153.4 | 133.6
Total other expense | $ 0.2 | $ (0.5) | $ (0.7) | $ (0.8) | $ (1.0) | $ 0.3 | $ (4.9) | $ (2.2) | $ (1.8) | (7.8) | $ 2.6 | $ 0.7
Equipment [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Estimated useful lives, in years |  |  |  |  |  |  |  |  | 5 years |  |  |
Equipment [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Estimated useful lives, in years |  |  |  |  |  |  |  |  | 7 years |  |  |
Leasehold Improvements [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Estimated useful lives, in years |  |  |  |  |  |  |  |  | 3 years |  |  |
Leasehold Improvements [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Estimated useful lives, in years |  |  |  |  |  |  |  |  | 10 years |  |  |
Overstated [Member] |  |  |  |  |  |  |  |  |  |  |  |
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Total costs and expenses |  |  |  |  |  |  |  |  |  | 0.8 |  |
Understated [Member] |  |  |  |  |  |  |  |  |  |  |  |
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Operating income (loss) |  |  |  |  |  |  |  |  |  | 0.8 |  |
Total other expense |  |  |  |  |  |  |  |  |  | $ 0.8 |  |

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