Earnings Per Share (Earnings Per Share Computation) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings per common share
Net income (loss) attributable to ExxonMobil (millions of dollars)	$ (680)	$ 3,170	$ (2,370)	$ 8,650
Weighted average number of common shares outstanding (millions of shares)	4,271	4,271	4,270	4,270
Earnings (Loss) per common share (dollars)	$ (0.15)	$ 0.75	$ (0.55)	$ 2.03
Dividends paid per common share (dollars)	$ 0.87	$ 0.87	$ 2.61	$ 2.56