Components of Comprehensive Income, Net of Related Tax (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 470.1	$ 359.4
Other comprehensive income (loss) (OCI):
Unrealized gains on derivative contracts	22.3	51.4
Tax effect	(4.1)	(10.0)
Net current period OCI, unrealized losses on derivative contracts	18.2	41.4
Unrealized losses on marketable debt securities	(6.6)	(2.1)
Tax effect	1.6	0.5
Net current period OCI, unrealized gains and (losses) on marketable debt securities	(5.0)	(1.6)
Pension plans	12.9	31.1
Tax effect	(3.1)	(7.6)
Net current period OCI, pension plans	9.8	23.5
Foreign currency translation losses	(89.1)	(347.1)
Net other comprehensive income (loss)	(66.1)	(283.8)
Comprehensive income	$ 404.0	$ 75.6