Components of Comprehensive Income (Loss), Net of Related Tax (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 373.0	$ 481.3	$ 683.3	$ (113.3)
Other comprehensive income (loss) (OCI):
Unrealized gains (losses) on derivative contracts	11.6	9.5	(2.0)	2.9
Unrealized gains on derivative contracts, tax	(3.1)	(2.6)	0.9	(0.5)
Net current period OCI, unrealized (losses) gain on derivative contracts	8.5	6.9	(1.1)	2.4
Unrealized (losses) gains on marketable debt securities	(0.5)	2.6	2.9	5.8
Unrealized gains (losses)on marketable debt securities, tax	0.1	(0.8)	(1.2)	(1.8)
Net current period OCI, unrealized (losses) gains on marketable debt securities	(0.4)	1.8	1.7	4.0
Pension plans, before tax	(1.4)	15.4	2.5	22.4
Pension plans, tax	0.0	(4.8)	(1.3)	(7.2)
Net current period OCI, pension plans	(1.4)	10.6	1.2	15.2
Foreign currency translation gains (losses)	126.1	(57.2)	201.1	68.3
Net other comprehensive income (loss)	132.8	(37.9)	202.9	89.9
Comprehensive income (loss)	$ 505.8	$ 443.4	$ 886.2	$ (23.4)