Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Income Taxes [Line Items]
Document Period End Date		Dec. 31, 2018
Operating loss carryforwards		$ 216.7
Unrecognized tax benefits		1,342.8	$ 1,180.4	[1]	$ 924.1
Reasonably possible amount of unrecognized tax benefits decrease within the next 12 months - minimum		900.0
Effective tax rate adjustment		940.0
Accrued interest and penalties related to income tax matters		152.0	155.3
Provision for income taxes, interest and penalties expense related to tax matters	$ 13.9		34.9		$ 41.7
Tax Cuts and Jobs Act of 2017 Transition Tax for Accumulated Foreign Earnings Liability, Noncurrent			1,200.0
Adjustments to Provisional Amounts Recorded at December 31, 2017 (Tax Cuts and Jobs Act of 2017)		$ 75.0
US net deferred tax liability remeasurement, amount			$ 500.0
Statutory U.S. federal income tax rate	21.00%	21.00%	35.00%		35.00%
Indefinite [Member]
Income Taxes [Line Items]
Operating loss carryforwards		$ 136.6

[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.