Components of Comprehensive Income, Net of Related Tax (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 377.7	$ 385.5	$ 1,340.7	$ 892.6
Other comprehensive income (loss) (OCI):
Unrealized gains (losses) on derivative contracts	8.2	(17.9)	29.4	1.3
Tax effect	(1.6)	3.4	(7.6)	0.6
Net current period OCI, unrealized gains (losses) on derivative contracts	6.6	(14.5)	21.8	1.9
Unrealized (losses) gains on marketable debt securities	(3.4)	0.0	(12.2)	12.4
Tax effect	0.7	0.0	2.9	(3.0)
Net current period OCI, unrealized gains and (losses) on marketable debt securities	(2.7)	0.0	(9.3)	9.4
Pension plans	22.7	3.4	49.0	45.7
Tax effect	(5.4)	(0.6)	(11.6)	(10.8)
Net current period OCI, pension plans	17.3	2.8	37.4	34.9
Foreign currency translation (losses) gains	(136.8)	112.6	(144.8)	(135.1)
Net other comprehensive (loss) income	(115.6)	100.9	(94.9)	(88.9)
Comprehensive income	$ 262.1	$ 486.4	$ 1,245.8	$ 803.7