Other Comprehensive Income Information (Schedule Of Accumulated Other Comprehensive Income Information) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other Comprehensive Income Foreign Currency Transaction And Translation Adjustment Net Of Tax Period Increase Decrease [Abstract]
Current period change excluding amounts reclassified from accumulated other comprehensive income, Cumulative Foreign Exchange Translation Adjustment	$ (5,649)	$ 749
Other Comprehensive Income Defined Benefit Plans Adjustment Net Of Tax Period Increase Decrease [Abstract]
Current period change excluding amounts reclassified from accumulated other comprehensive income, Postretirement Benefits Reserves Adjustment	87	(26)
Amounts reclassified from accumulated other comprehensive income, Postretirement Benefits Reserves Adjustment	204	185
Other Comprehensive Income Loss Net Of Tax Period Change [Abstract]
Beginning Balance, Total	(19,493)
Ending Balance, Total	(24,339)
Exxon Mobil Corporation Share After Noncontrolling Interest [Member]
Other Comprehensive Income Foreign Currency Transaction And Translation Adjustment Net Of Tax Period Increase Decrease [Abstract]
Beginning Balance, Cumulative Foreign Exchange Translation Adjustment	(12,446)	(13,881)
Current period change excluding amounts reclassified from accumulated other comprehensive income, Cumulative Foreign Exchange Translation Adjustment	(5,113)	627
Total change in accumulated other comprehensive income, Cumulative Foreign Exchange Translation Adjustment	(5,113)	627
Ending Balance, Cumulative Foreign Exchange Translation Adjustment	(17,559)	(13,254)
Other Comprehensive Income Defined Benefit Plans Adjustment Net Of Tax Period Increase Decrease [Abstract]
Beginning Balance, Postretirement Benefits Reserves Adjustment	(7,047)	(5,683)
Current period change excluding amounts reclassified from accumulated other comprehensive income, Postretirement Benefits Reserves Adjustment	72	(23)
Amounts reclassified from accumulated other comprehensive income, Postretirement Benefits Reserves Adjustment	195	178
Total change in accumulated other comprehensive income, Postretirement Benefits Reserves Adjustment	267	155
Ending Balance, Postretirement Benefits Reserves Adjustment	(6,780)	(5,528)
Other Comprehensive Income Loss Net Of Tax Period Change [Abstract]
Beginning Balance, Total	(19,493)	(19,564)
Current period change excluding amounts reclassified from accumulated other comprehensive income, Total	(5,041)	604
Amounts reclassified from accumulated other comprehensive income, Total	195	178
Total change in accumulated other comprehensive income, Total	(4,846)	782
Ending Balance, Total	$ (24,339)	$ (18,782)