Pension And Other Postretirement Benefits (Summary Of The Change In Accumulated Other Comprehensive Income) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Total (charge)/credit to other comprehensive income, before tax	$ (4,619)	$ 7,281	$ (1,523)
(Charge)/credit to income tax (see Note 4)	1,549	(2,336)	393
(Charge)/credit to investment in equity companies	(81)	49	(49)
(Charge)/credit to other comprehensive income including noncontrolling interests, after tax	(3,151)	4,994	(1,179)
Charge/(credit) to equity of noncontrolling interests	85	(279)	(124)
(Charge)/credit to other comprehensive income attributable to ExxonMobil	(3,066)	4,715	(1,303)
Pension Benefits - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Total (charge)/credit to other comprehensive income, before tax	(1,776)	2,678	(969)
Pension Benefits - Non-U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Total (charge)/credit to other comprehensive income, before tax	(1,463)	3,054	253
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Total (charge)/credit to other comprehensive income, before tax	$ (1,380)	$ 1,549	$ (807)