Income Taxes - Narrative (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Net tax provision	$ 330.5	$ 95.6	$ 132.6
Tax Cuts And Jobs Act Of 2017,incomplete accounting, change In tax rate, deferred tax asset, provisional income tax expense	41.1
Foreign net operating losses	151.2
State net operating loss carry forwards	21.9
State tax credits	12.1
Increase (decrease) in valuation allowance	21.5
Undistributed earnings of foreign subsidiaries	$ 3,500.0
Statutory federal tax rate	35.00%	35.00%	35.00%
Decrease in unrecognized tax benefit related to expiration of statute of limitations and settlement of audits	$ 51.7
Net increase in unrecognized tax benefit during the year		$ 31.3
Decrease in income tax provision if unrecognized tax benefits were recognized	187.7
Unrecognized interest and penalties	14.8	12.0	$ 4.0
Unrecognized penalties	4.5	3.7	0.7
Change in interest and penalties in tax accruals for uncertainties	4.0	5.6	0.6
Unrecognized tax benefits	214.3	$ 162.6	$ 131.3	$ 18.9
Minimum
Income Tax Contingency [Line Items]
Reduction in unrecognized tax benefit in the next 12 months	$ 0.0
Examination of income tax return	3 years
Income tax return in foreign jurisdictions	3 years
Maximum
Income Tax Contingency [Line Items]
Reduction in unrecognized tax benefit in the next 12 months	$ 53.0
Examination of income tax return	5 years
Income tax return in foreign jurisdictions	5 years
Federal
Income Tax Contingency [Line Items]
Tax credit carryforwards amount	$ 98.8
State And Local Jurisdiction
Income Tax Contingency [Line Items]
State net operating loss carry forwards	738.6
Tax credit carryforwards amount	$ 15.4
State And Local Jurisdiction | Minimum
Income Tax Contingency [Line Items]
Operating loss carryforwards expiration, years	1 year
State And Local Jurisdiction | Maximum
Income Tax Contingency [Line Items]
Operating loss carryforwards expiration, years	20 years
Foreign Country
Income Tax Contingency [Line Items]
Foreign net operating loss carryforwards	$ 650.3
Tax credit carryforwards amount	2.6
Domestic Tax Authority [Member]
Income Tax Contingency [Line Items]
Unrecognized tax benefits	$ 204.7