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, 2018	Mar. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Foreign currency cumulative translation adjustments, Before Tax	$ 83.5	$ 54.4
Unrealized cash flow hedge (losses), Before Tax	(33.1)	(36.6)
Reclassification adjustments on cash flow hedges, Before Tax	11.2	(11.0)
Adjustments to prior service cost and unrecognized actuarial assumptions, Before Tax	(24.7)	(3.7)
Total Other Comprehensive Income (Loss), Before Tax	36.9	3.1
Foreign currency cumulative translation adjustments, Tax	(11.3)	5.4
Unrealized cash flow hedge (losses), Tax	(6.7)	(10.3)
Reclassification adjustments on cash flow hedges, Tax	1.5	(2.0)
Adjustments to prior service cost and unrecognized actuarial assumptions, Tax	(21.4)	(0.2)
Total Other Comprehensive Income (Loss), Tax	(37.9)	(7.1)
Foreign currency cumulative translation adjustments, net of tax	94.8	49.0
Unrealized cash flow hedge (losses), net of tax	(26.4)	(26.3)
Reclassification adjustments on cash flow hedges, net of tax	9.7	(9.0)
Adjustments to prior service cost and unrecognized actuarial assumptions, net of tax	(3.3)	(3.5)
Total Other Comprehensive Income	$ 74.8	$ 10.2