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Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Valuation Allowance for Doubtful Accounts [Member] |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | $ 1.8 | $ 5.2 | $ 4.1
Additions Acquisition Beginning Balance |  | 0.2 |
Additions Charged to Costs and Expenses | 0.1 | (0.7) | 1.4
Deductions & Write-offs | 0.1 | (2.9) | (0.3)
Balance at End of Year | 2.0 | 1.8 | 5.2
Valuation Allowance for Sales Returns [Member] |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | 1.4 | 1.0 | 1.3
Additions Charged to Costs and Expenses | 0.3 | 0.2 | 0.1
Deductions & Write-offs | 0.1 | 0.2 | (0.4)
Balance at End of Year | 1.8 | 1.4 | 1.0
Valuation Allowance on Deferred Tax Asset [Member] |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | 27.4 | 17.9 | 13.6
Additions Acquisition Beginning Balance |  | 5.9 |
Additions Charged to Costs and Expenses | 4.2 | 4.9 | 4.8
Deductions & Write-offs | (1.0) | (1.3) | (0.5)
Balance at End of Year | $ 30.6 | $ 27.4 | $ 17.9

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