Stockholders' Equity - Components of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 11,384.4	$ 1,826.4	$ 1,854.9
Total other comprehensive income (loss), net of tax	281.7	(211.0)	(39.4)
Ending balance	14,181.3	11,384.4	1,826.4
Cumulative Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(607.9)	(411.7)
Other comprehensive (loss) income before reclassifications	201.7	(198.0)
Amounts reclassified to earnings	87.4	1.8
Total other comprehensive income (loss), net of tax	289.1	(196.2)
Ending balance	(318.8)	(607.9)	(411.7)
Pension and Postretirement Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(400.0)	(422.3)
Other comprehensive (loss) income before reclassifications	6.6	10.0
Amounts reclassified to earnings	7.9	12.3
Total other comprehensive income (loss), net of tax	14.5	22.3
Ending balance	(385.5)	(400.0)	(422.3)
Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(36.9)	0.2
Other comprehensive (loss) income before reclassifications	(27.8)	(48.0)
Amounts reclassified to earnings	5.9	10.9
Total other comprehensive income (loss), net of tax	(21.9)	(37.1)
Ending balance	(58.8)	(36.9)	0.2
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,044.8)	(833.8)	(794.4)
Other comprehensive (loss) income before reclassifications	180.5	(236.0)
Amounts reclassified to earnings	101.2	25.0
Total other comprehensive income (loss), net of tax	281.7	(211.0)
Ending balance	$ (763.1)	$ (1,044.8)	$ (833.8)