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Nature of Business and Summary of Significant Accounting Policies - Summary of Assets and Liabilities that are Measured at Fair Value on a Recurring Basis (Detail) - Fair Value, Recurring [Member] - USD ($) $ in Millions | Jun. 30, 2021 | Jun. 30, 2020
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Cash, cash equivalents, and restricted cash [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Assets, Fair Value Disclosure [Abstract] |  |
Assets, Fair Value Disclosure | $ 102.4 | $ 120.0
Cash, cash equivalents, and restricted cash [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Assets, Fair Value Disclosure [Abstract] |  |
Assets, Fair Value Disclosure | 0.0 | 0.0
Cash, cash equivalents, and restricted cash [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Assets, Fair Value Disclosure [Abstract] |  |
Assets, Fair Value Disclosure | 0.0 | 0.0
Discretionary retirement plan [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Assets, Fair Value Disclosure [Abstract] |  |
Assets, Fair Value Disclosure | 3.4 | 2.4
Liabilities, Fair Value Disclosure [Abstract] |  |
Financial and Nonfinancial Liabilities, Fair Value Disclosure | 3.4 | 2.4
Discretionary retirement plan [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Assets, Fair Value Disclosure [Abstract] |  |
Assets, Fair Value Disclosure | 0.8 | 1.1
Liabilities, Fair Value Disclosure [Abstract] |  |
Financial and Nonfinancial Liabilities, Fair Value Disclosure | 0.8 | 1.1
Discretionary retirement plan [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Assets, Fair Value Disclosure [Abstract] |  |
Assets, Fair Value Disclosure | 0.0 | 0.0
Liabilities, Fair Value Disclosure [Abstract] |  |
Financial and Nonfinancial Liabilities, Fair Value Disclosure | $ 0.0 | $ 0.0

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