Reconciliation of Beginning and Ending Amounts of Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, beginning balance	$ 1,180.4	[1]	$ 924.1
Decreases for positions taken in prior years	(64.1)		(13.7)
Increases for positions taken in prior years	180.8		143.9
Increases for positions related to the current year	75.1		140.2
Settlements with taxing authorities	(24.1)		(6.5)
Lapsing of statutes of limitations	(5.3)		(7.6)
Unrecognized tax benefits	$ 1,342.8		$ 1,180.4	[1]

[1] Of this amount, $1,313.7 million and $1,132.3 million are included in Other long-term liabilities for 2018 and 2017, respectively, and $12.5 million and $30.8 million are included in Prepaid expenses and other current assets for 2018 and 2017, respectively, on the Consolidated Balance Sheet. The remainder is included in Deferred income taxes on the Consolidated Balance Sheet.