Contingent Liabilities - Additional Information (Detail) € in Millions, Vehicle in Millions							1 Months Ended	3 Months Ended			12 Months Ended
	Mar. 05, 2019 USD ($)	Mar. 05, 2019 EUR (€)	Nov. 22, 2017 USD ($)	Nov. 22, 2017 EUR (€)	Jun. 29, 2016 Vehicle Claim	Jun. 09, 2011 Facility	Apr. 30, 2016 Purchaser	Mar. 31, 2019 USD ($) Defendant	Dec. 31, 2018 USD ($)	Dec. 31, 2018 EUR (€)	Dec. 31, 2017 USD ($)	Dec. 31, 2017 EUR (€)
Loss Contingencies [Line Items]
Fine due period after investigation resolved								90 days
Number of defendants in antitrust class actions								19
United States District Court for Eastern District of Michigan
Loss Contingencies [Line Items]
Number of pending antitrust class actions								15
Ontario and Quebec Superior Court
Loss Contingencies [Line Items]
Number of pending antitrust class actions								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
Litigation with European Commission
Loss Contingencies [Line Items]
Number of facilities visited | Facility						2
Loss contingency, accrual	$ 203,000,000	€ 179.0	$ 9,700,000	€ 8.1					$ 210,000,000	€ 184.0	$ 9,900,000	€ 8.3
End-payor Settlement Class | United States District Court for Eastern District of Michigan
Loss Contingencies [Line Items]
Number of purchaser opt for end-payor class settlements | Purchaser							1