Other Comprehensive Income Information (Schedule Of Accumulated Other Comprehensive Income Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 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	$ 1,469	$ (1,424)	$ (1,305)	$ (75)
Adjustment for foreign exchange translation (gain)/loss included in net income	14	0	14	0
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	(140)	103	(189)	43
Amounts reclassified from accumulated other comprehensive income, Postretirement Benefits Reserves Adjustment	206	186	613	512
Other Comprehensive Income Loss Net Of Tax Period Change [Abstract]
Beginning Balance, Total			(19,493)
Ending Balance, Total	(20,189)		(20,189)
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			(1,125)	(252)
Adjustment for foreign exchange translation (gain)/loss included in net income			14	0
Total change in accumulated other comprehensive income, Cumulative Foreign Exchange Translation Adjustment			(1,111)	(252)
Ending Balance, Cumulative Foreign Exchange Translation Adjustment	(13,557)	(14,133)	(13,557)	(14,133)
Net investment hedge gain/(loss), net of taxes			(159)
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			(172)	48
Amounts reclassified from accumulated other comprehensive income, Postretirement Benefits Reserves Adjustment			587	491
Total change in accumulated other comprehensive income, Postretirement Benefits Reserves Adjustment			415	539
Ending Balance, Postretirement Benefits Reserves Adjustment	(6,632)	(5,144)	(6,632)	(5,144)
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			(1,297)	(204)
Amounts reclassified from accumulated other comprehensive income, Total			601	491
Total change in accumulated other comprehensive income, Total			(696)	287
Ending Balance, Total	$ (20,189)	$ (19,277)	$ (20,189)	$ (19,277)