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, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Foreign currency cumulative translation adjustments, Before Tax	$ 7.9	$ 83.5
Unrealized cash flow hedge gains (losses), Before Tax	16.7	(33.1)
Reclassification adjustments on cash flow hedges, Before Tax	(9.9)	11.2
Adjustments to prior service cost and unrecognized actuarial assumptions, Before Tax	3.5	(4.1)
Total Other Comprehensive Income (Loss), Before Tax	18.2	57.5
Foreign currency cumulative translation adjustments, Tax	12.3	(11.3)
Unrealized cash flow hedge gains (losses), Tax	2.2	(6.7)
Reclassification adjustments on cash flow hedges, Tax	(1.7)	1.5
Adjustments to prior service cost and unrecognized actuarial assumptions, Tax	1.5	(0.8)
Total Other Comprehensive Income (Loss), Tax	14.3	(17.3)
Foreign currency cumulative translation adjustments, net of tax	(4.4)	94.8
Unrealized cash flow hedge gains (losses), net of tax	14.5	(26.4)
Reclassification adjustments on cash flow hedges, net of tax	(8.2)	9.7
Adjustments to prior service cost and unrecognized actuarial assumptions, net of tax	2.0	(3.3)
Total Other Comprehensive Income	$ 3.9	$ 74.8