Components of Comprehensive Income, Net of Related Tax (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 385.5	$ 607.9	$ 892.6	$ 1,856.6
Other comprehensive (loss) income (OCI):
Unrealized (losses) gains on derivative contracts	(17.9)	(13.6)	1.3	(30.0)
Tax effect	3.4	3.8	0.6	8.2
Net current period OCI, unrealized losses on derivative contracts	(14.5)	(9.8)	1.9	(21.8)
Unrealized gains on marketable debt securities	0.0	0.1	12.4	11.6
Tax effect	0.0	0.1	(3.0)	(2.8)
Net current period OCI, unrealized gains and (losses) on marketable debt securities	0.0	0.2	9.4	8.8
Pension plans	3.4	11.0	45.7	21.1
Tax effect	(0.6)	(2.7)	(10.8)	(5.0)
Net current period OCI, pension plans	2.8	8.3	34.9	16.1
Foreign currency translation gains (losses)	112.6	(126.5)	(135.1)	(94.6)
Net other comprehensive income (loss)	100.9	(127.8)	(88.9)	(91.5)
Comprehensive income	$ 486.4	$ 480.1	$ 803.7	$ 1,765.1