Accumulated Other Comprehensive Income - Tax Effects on Each Component of Accumulated Other Comprehensive Income Recognized in Statements of Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
Foreign currency cumulative translation adjustments, before tax	$ 0.6	$ (29.2)
Unrealized cash flow hedge gains, before tax	47.5	65.7
Reclassification adjustments on cash flow hedges, before tax	(0.9)	(15.4)
Adjustments to prior service cost and unrecognized actuarial assumptions, before tax	1.5	1.7
Total Other Comprehensive Income (Loss), before tax	48.7	22.8
Foreign currency cumulative translation adjustments, tax	19.7	25.0
Unrealized cash flow hedge gains, tax	7.6	10.9
Reclassification adjustments on cash flow hedges, tax	(0.4)	(1.9)
Adjustments to prior service cost and unrecognized actuarial assumptions, tax	0.7	2.0
Total Other Comprehensive Income (Loss), tax	27.6	36.0
Foreign currency cumulative translation adjustments, net of tax	(19.1)	(54.2)
Unrealized cash flow hedge gains, net of tax	39.9	54.8
Reclassification adjustments on hedges, net of tax	(0.5)	(13.5)
Adjustments to prior service cost and unrecognized actuarial assumptions, net of tax	0.8	(0.3)
Total Other Comprehensive Income (Loss)	$ 21.1	$ (13.2)