Earnings Per Share (Earnings Per Share Computation) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Earnings per common share
Net income attributable to ExxonMobil	$ 9,100		$ 9,500
Weighted average number of common shares outstanding	4,328		4,485
Earnings per common share (dollars)	$ 2.10	[1]	$ 2.12	[1]

[1] The calculation of earnings per common share and earnings per common share-assuming dilution are the same in each period.