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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Foreign currency cumulative translation adjustments, Before Tax	$ 145.0	$ 58.3	$ 414.6	$ 113.9
Unrealized cash flow hedge (losses) gains, Before Tax	(35.9)	(16.1)	(99.0)	(80.9)
Reclassification adjustments on cash flow hedges, Before Tax	5.2	(17.7)	(11.6)	(75.2)
Unrealized gains on securities, Before Tax				0.4
Adjustments to prior service cost and unrecognized actuarial assumptions, Before Tax	0.5	2.2	(2.9)	25.6
Total Other Comprehensive Income (Loss), Before Tax	114.8	26.7	301.1	(16.2)
Foreign currency cumulative translation adjustments, Tax	15.3		46.7
Unrealized cash flow hedge (losses) gains, Tax	(7.6)	(6.4)	(19.6)	(27.9)
Reclassification adjustments on cash flow hedges, Tax	1.1	(3.8)	(2.2)	(17.2)
Unrealized gains on securities, Tax				0.0
Adjustments to prior service cost and unrecognized actuarial assumptions, Tax	1.5	1.0	2.1	3.3
Total Other Comprehensive Income (Loss), Tax	10.3	(9.2)	27.0	(41.8)
Foreign currency cumulative translation adjustments, net of tax	129.7	58.3	367.9	113.9
Unrealized cash flow hedge (losses) gains, net of tax	(28.3)	(9.7)	(79.4)	(53.0)
Reclassification adjustments on cash flow hedges, net of tax	4.1	(13.9)	(9.4)	(58.0)
Unrealized gains on securities, net of tax				0.4
Adjustments to prior service cost and unrecognized actuarial assumptions, net of tax	(1.0)	1.2	(5.0)	22.3
Total Other Comprehensive Income	$ 104.5	$ 35.9	$ 274.1	$ 25.6