Income Tax Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Federal Income Tax Note
Tax Cuts and Jobs Act, Change in Tax Rate, Deferred Tax Liability, Income Tax Benefit			$ 97.9
Tax Cuts and Jobs Act, Transition Tax for Accumulated Foreign Earnings, Income Tax Expense			66.4
Tax Cuts and Jobs Act, Measurement Period Adjustment, Income Tax Expense (Benefit)		$ 11.5
Tax Cuts and Jobs Act of 2017, Complete Accounting, Undistributed Accumulated Earnings of Foreign Subsidiary for which Unrecognized Deferred Tax Liabilities Have Not Been Recorded	$ 700.0
Increases (Decreases) to Tax Positions Taken During Prior Years	(21.1)	261.5	0.3
Unrecognized Tax Benefits, Interest on Income Taxes Expense	12.8
Valuation Allowance on Deferred Tax Assets	28.3	18.4
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	9.9	(1.9)
Income Taxes Paid, Net	35.1	139.7	$ 377.0
U.S. Federal
Federal Income Tax Note
Operating Loss Carryforwards	10.6	6.5
State and Local Jurisdiction
Federal Income Tax Note
Operating Loss Carryforwards	183.0
Subsidiary Return | U.S. Federal
Federal Income Tax Note
Operating Loss Carryforwards	$ 0.7	0.7
Tax Year 2017
Federal Income Tax Note
Increases (Decreases) to Tax Positions Taken During Prior Years		$ 261.1