Components of Comprehensive Income, Net of Related Tax (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 607.9	$ 545.3	$ 1,856.6	$ 1,617.0
Other comprehensive (loss) income (OCI):
Unrealized losses on derivative contracts	(13.6)	(8.9)	(30.0)	(6.2)
Tax effect	3.8	2.5	8.2	2.1
Net current period OCI, unrealized losses on derivative contracts	(9.8)	(6.4)	(21.8)	(4.1)
Unrealized gains (losses) on marketable debt securities	0.1	(1.5)	11.6	(3.6)
Tax effect	0.1	0.4	(2.8)	0.9
Net current period OCI, unrealized gains and (losses) on marketable debt securities	0.2	(1.1)	8.8	(2.7)
Pension plans	11.0	10.2	21.1	34.1
Tax effect	(2.7)	(2.4)	(5.0)	(8.2)
Net current period OCI, pension plans	8.3	7.8	16.1	25.9
Foreign currency translation losses	(126.5)	(1.6)	(94.6)	(120.5)
Net other comprehensive (loss) income	(127.8)	(1.3)	(91.5)	(101.4)
Comprehensive income	$ 480.1	$ 544.0	$ 1,765.1	$ 1,515.6