Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year		$ 10.1	$ 8.7	$ 10.0
Amounts Recorded in Earnings		7.0	6.6	4.2
Adjustments	[1]	(8.8)	(5.2)	(5.5)
Balance at End of Year		8.3	10.1	8.7
Allowance for Estimated Policy Cancellations [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year		9.9	8.3	7.8
Amounts Recorded in Earnings		(1.3)	4.1	0.5
Adjustments	[2]	1.4	(2.5)
Balance at End of Year		10.0	9.9	8.3
Valuation Allowance for Deferred Tax Assets [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year		94.9	80.5	67.4
Amounts Recorded in Earnings		60.0	14.4	13.1
Balance at End of Year		154.9	94.9	80.5
Accumulated Amortization of Expiration Lists, Non-compete Agreements and Trade Names [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year		2,537.0	2,087.5	1,750.4
Amounts Recorded in Earnings		415.1	417.3	334.0
Adjustments	[3]	(28.1)	32.2	3.1
Balance at End of Year		$ 2,924.0	$ 2,537.0	$ 2,087.5

[1] Net activity of bad debt write offs and recoveries and acquired businesses.

[2] Additions to allowance related to acquired businesses.

[3] Elimination of fully amortized expiration lists, non-compete agreements and trade names, intangible asset/amortization reclassifications and disposal of acquired businesses.