Components of Comprehensive Income, Net of Related Tax (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 359.4	$ 629.0
Other comprehensive income (loss) (OCI):
Unrealized gains (losses) on derivative contracts	51.4	(15.8)
Tax effect	(10.0)	4.2
Net current period OCI, unrealized losses on derivative contracts	41.4	(11.6)
Unrealized (losses) gains on marketable debt securities	(2.1)	6.2
Tax effect		(1.6)
Net current period OCI, unrealized gains and (losses) on marketable debt securities	(1.6)	4.6
Pension plans	31.1	0.7
Tax effect	(7.6)	(0.1)
Net current period OCI, pension plans	23.5	0.6
Foreign currency translation (losses) gains	(347.1)	9.4
Net other comprehensive (loss) income	(283.8)	3.0
Comprehensive income	$ 75.6	$ 632.0