Contingent Liabilities - Additional Information (Detail) € in Millions, Vehicle in Millions, R$ in Millions					1 Months Ended						3 Months Ended	9 Months Ended	12 Months Ended
	Nov. 22, 2017 USD ($)	Nov. 22, 2017 EUR (€)	Jun. 29, 2016 Vehicle Claim	Jun. 09, 2011 Facility	Sep. 30, 2017 USD ($)	Sep. 30, 2017 BRL (R$)	Apr. 30, 2016 Purchaser	Mar. 31, 2015 USD ($)	Oct. 31, 2014 USD ($)	Oct. 31, 2014 BRL (R$)	Mar. 31, 2018	Sep. 30, 2018 USD ($) Defendant	Dec. 31, 2017 USD ($)	Dec. 31, 2017 EUR (€)	Dec. 31, 2016 USD ($)	Dec. 31, 2014 USD ($)
Loss Contingencies [Line Items]
Number of defendants in antitrust class actions | Defendant												19
Litigation with European Commission
Loss Contingencies [Line Items]
Number of facilities visited | Facility				2
Loss contingency, accrual	$ 9,700,000	€ 8.1											$ 9,900,000	€ 8.3
Litigation with Competition Commission Of South Africa
Loss Contingencies [Line Items]
Loss contingency, accrual												$ 5,000,000			$ 6,000,000
Settlement agreement, date												September 2017
Settlement agreements amount					$ 11,000,000	R$ 150
Litigation with General Superintendence of Administrative Council for Economic Defense in Brazil
Loss Contingencies [Line Items]
Settlement agreement, date												November 2016
Brazilian Subsidiaries
Loss Contingencies [Line Items]
Aggregate assessment for all alleged violations									$ 21,000,000	R$ 81
Brazilian Subsidiaries | Maximum
Loss Contingencies [Line Items]
Reduce in penalties associated with eligible tax matters, percentage											85.00%
United States District Court for Eastern District of Michigan
Loss Contingencies [Line Items]
Settlement agreements amount								$ 81,000,000
Number of pending antitrust class actions | Defendant												15
Expense related settlement agreements								$ 77,000,000								$ 65,000,000
United States District Court for Eastern District of Michigan | End-payor settlement class
Loss Contingencies [Line Items]
Number of purchaser opt for end-payor class settlements | Purchaser							1
United States District Court for Eastern District of Michigan | Direct purchaser settlement class
Loss Contingencies [Line Items]
Expense related settlement agreements																$ 60,500,000
Number of purchaser opt for direct purchaser class settlement | Purchaser							2
Ontario and Quebec Superior Court
Loss Contingencies [Line Items]
Number of pending antitrust class actions | Defendant												4
Damages from Product Defects
Loss Contingencies [Line Items]
Number of vehicles recalled | Vehicle			1.4
Number of confirmed incidents | Claim			8
Damages from Product Defects | Maximum
Loss Contingencies [Line Items]
Range of possible loss												$ 20,000,000