Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings per common share
Net income (loss) attributable to ExxonMobil	$ (22,440)	$ 14,340	$ 20,840
Weighted average number of common shares outstanding	4,271	4,270	4,270
Earnings (Loss) per common share (dollars)	$ (5.25)	$ 3.36	$ 4.88
Dividends paid per common share (dollars)	$ 3.48	$ 3.43	$ 3.23