Litigation (Details) $ in Millions					12 Months Ended
	Mar. 27, 2017 defendant	Nov. 13, 2013 USD ($)	Aug. 03, 2012 USD ($)	Feb. 14, 2011 USD ($)	Dec. 31, 1991 USD ($)	Mar. 31, 2019 LegalMatter	Jan. 03, 2012
MTBE | Pending Litigation
Loss Contingencies [Line Items]
Pending lawsuits and claims (in number of claims) | LegalMatter						6
Ecuador | Declaratory Relief Claim
Loss Contingencies [Line Items]
Pending lawsuits and claims (in number of claims) | LegalMatter						1
Ecuador | Pending Litigation
Loss Contingencies [Line Items]
Conducted remediation program					3 years
Remediation program					$ 40
Amount assessed in damages		$ 9,500		$ 8,600
Amount assessed for plaintiffs representatives				900
Additional amount assessed in punitive damages				$ 8,600
Public apology date within judgment/clarification ruling (in days)				15 days
Proposed additional payment for plaintiff attorney fees as percentage of judgment							0.10%
Litigation settlement, amount awarded to			$ 19,100
Writ of Certiorari
Loss Contingencies [Line Items]
Number of defendants | defendant	2