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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Foreign currency cumulative translation adjustments, Before Tax	$ (41.6)	$ (45.4)	$ (25.6)	$ (136.0)
Unrealized cash flow hedge gains, Before Tax	33.6	38.1	46.4	67.7
Reclassification adjustments on cash flow hedges, Before Tax	(11.2)	5.0	(28.2)	26.9
Adjustments to prior service cost and unrecognized actuarial assumptions, Before Tax	3.7	1.0	10.8	1.0
Total Other Comprehensive (Loss) Income, Before Tax	(15.5)	(1.3)	3.4	(40.4)
Foreign currency cumulative translation adjustments, Tax	29.2	(1.4)	34.5	(9.0)
Unrealized cash flow hedge gains, Tax	7.5	5.3	5.4	9.7
Reclassification adjustments on cash flow hedges, Tax	(1.5)	0.9	(4.1)	3.9
Adjustments to prior service cost and unrecognized actuarial assumptions, Tax	0.7	(1.0)	3.4	(3.0)
Total Other Comprehensive (Loss) Income, Tax	35.9	3.8	39.2	1.6
Foreign currency cumulative translation adjustments, net of tax	(70.8)	(44.0)	(60.1)	(127.0)
Unrealized cash flow hedge gains, net of tax	26.1	32.8	41.0	58.0
Reclassification adjustments on cash flow hedges, net of tax	(9.7)	4.1	(24.1)	23.0
Adjustments to prior service cost and unrecognized actuarial assumptions, net of tax	3.0	2.0	7.4	4.0
Total Other Comprehensive (Loss) Income	$ (51.4)	$ (5.1)	$ (35.8)	$ (42.0)