Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 1,675.2	$ 521.7	$ 1,604.0
Unrealized (losses) gains on derivative contracts
Net (loss) gain arising during the period	(125.5)	(6.5)	38.7
Tax effect	33.9	6.7	(10.8)
Reclassification adjustment	133.4	10.8	(29.3)
Tax effect	(36.3)	(8.9)	8.5
Net current period OCI, unrealized gains and (losses) on derivative contracts	5.5	2.1	7.1
Unrealized (losses) gains on marketable debt securities
Net holding loss	(1.5)	(0.1)	(2.3)
Tax effect	0.4	0.4	0.6
Reclassification adjustment	(0.6)	(3.7)	(2.1)
Tax effect	0.2	1.0	0.6
Net current period OCI, unrealized gains and (losses) on marketable debt securities	(1.5)	(2.4)	(3.2)
Pension plans
Net gain (loss) arising during the period	37.1	(50.3)	17.7
Tax effect	(16.7)	7.7	(2.6)
Reclassification adjustment	26.6	28.9	42.4
Tax effect	(8.5)	(10.0)	(14.8)
Net current period OCI, pension plans	38.5	(23.7)	42.7
Foreign currency translation gain (loss)	292.0	(87.1)	(483.8)
Net other comprehensive income (loss)	334.5	(111.1)	(437.2)
Comprehensive Income	$ 2,009.7	$ 410.6	$ 1,166.8