Pension And Other Postretirement Benefits (Summary Of The Change In Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Total (charge)/credit to other comprehensive income, before tax	$ 1,657	$ 1,279	$ 2,287
(Charge)/credit to income tax (see Note 4)	(470)	(290)	(692)
(Charge)/credit to investment in equity companies	24	(43)	(16)
(Charge)/credit to other comprehensive income including noncontrolling interests, after tax	1,211	946	1,579
Charge/(credit) to equity of noncontrolling interests	(114)	12	24
Exxon Mobil Corporation Share After Noncontrolling Interest [Member]
Defined Benefit Plan Disclosure [Line Items]
Total change in accumulated other comprehensive income, Postretirement Benefits Reserves Adjustment	1,097	958	1,603
U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Total (charge)/credit to other comprehensive income, before tax	156	1,376	790
Pension Benefits - Non-U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Total (charge)/credit to other comprehensive income, before tax	823	63	824
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Total (charge)/credit to other comprehensive income, before tax	$ 678	$ (160)	$ 673