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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Foreign currency cumulative translation adjustments, before tax	$ (18.2)	$ 4.3	$ (17.6)	$ (24.9)
Unrealized cash flow hedge gains (losses), before tax	0.4	(27.6)	47.9	38.1
Reclassification adjustments on cash flow hedges, before tax	2.8	(15.0)	1.8	(30.4)
Adjustments to prior service cost and unrecognized actuarial assumptions, before tax	(1.8)	1.7	(0.3)	3.4
Total Other Comprehensive Income (Loss), before tax	(16.8)	(36.6)	31.8	(13.8)
Foreign currency cumulative translation adjustments, tax	(4.6)	(18.7)	15.1	6.3
Unrealized cash flow hedge gains (losses), before tax	(1.8)	(4.9)	5.8	6.0
Reclassification adjustments on cash flow hedges, tax	0.5	(1.9)		(3.8)
Adjustments to prior service cost and unrecognized actuarial assumptions, tax	(0.6)	(0.4)	0.1	1.6
Total Other Comprehensive Income (Loss), before tax	(6.5)	(25.9)	21.0	10.1
Foreign currency cumulative translation adjustments, net of tax	(13.6)	23.0	(32.7)	(31.2)
Unrealized cash flow hedge gains (losses), net of tax	2.2	(22.7)	42.1	32.1
Reclassification adjustments on hedges, net of tax	2.3	(13.1)	1.8	(26.6)
Adjustments to prior service cost and unrecognized actuarial assumptions, net of tax	(1.2)	2.1	(0.4)	1.8
Total Other Comprehensive Income (Loss)	$ (10.3)	$ (10.7)	$ 10.8	$ (23.9)