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Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
SEC Schedule, 12-09, Allowance, Credit Loss [Member] |  |  |
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | $ 13.5 | $ 12.8 | $ 13.3
Amounts Recorded in Earnings | 5.8 | 5.4 | 4.9
Adjustments | (9.3) | (4.7) | (5.4)
Balance at End of Year | 10.0 | 13.5 | 12.8
Allowance for Estimated Policy Cancellations [Member] |  |  |
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | 7.4 | 7.1 | 7.4
Amounts Recorded in Earnings | (1.2) | 2.1 | 0.2
Adjustments | 1.6 | (1.8) | (0.5)
Balance at End of Year | 7.8 | 7.4 | 7.1
Valuation Allowance for Deferred Tax Assets [Member] |  |  |
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | 79.1 | 66.8 | 52.8
Amounts Recorded in Earnings | (11.7) | 12.3 | 14.0
Balance at End of Year | 67.4 | 79.1 | 66.8
Accumulated Amortization of Expiration Lists, Noncompete Agreements and Trade Names [Member] |  |  |
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | 1,490.7 | 1,203.6 | 983.9
Amounts Recorded in Earnings | 291.3 | 264.7 | 247.2
Adjustments | (31.6) | 22.4 | (27.5)
Balance at End of Year | $ 1,750.4 | $ 1,490.7 | $ 1,203.6

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