Derivative Instruments and Hedging Activities - Schedule of Effects of Master Netting Agreements on Condensed Consolidated Balance Sheets (Detail) - Cash Flow Hedges [Member] - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Other Current Assets [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross Amount	$ 31.3	$ 14.5
Offset	11.7	13.4
Net Amount in Balance Sheet	19.6	1.1
Other Assets [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross Amount	21.1	4.8
Offset	2.6	4.3
Net Amount in Balance Sheet	18.5	0.5
Other Current Liabilities [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross Amount	13.0	45.8
Offset	11.7	13.4
Net Amount in Balance Sheet	1.3	32.4
Other Long-term Liabilities [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross Amount	2.6	22.8
Offset	$ 2.6	4.3
Net Amount in Balance Sheet		$ 18.5