Condensed Consolidated Statement Of Changes In Equity - USD ($) shares in Millions, $ in Millions	Total	ExxonMobil Share Of Common Stock [Member]	ExxonMobil Share Of Earnings Reinvested [Member]	ExxonMobil Share Of Accumulated Other Comprehensive Income [Member]	ExxonMobil Share Of Common Stock Held In Treasury [Member]	ExxonMobil Share Of Equity [Member]	Noncontrolling Interests [Member]
Balance at Dec. 31, 2018	$ 198,528	$ 15,258	$ 421,653	$ (19,564)	$ (225,553)	$ 191,794	$ 6,734
Balance (in shares) - issued at Dec. 31, 2018	8,019
Balance (in shares) - in treasury at Dec. 31, 2018	(3,782)
Balance (in shares) - outstanding at Dec. 31, 2018	4,237
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amortization of stock-based awards	$ 545	545				545
Other	267	(8)				(8)	275
Net income (loss) for the period	9,044		8,650			8,650	394
Dividends - common shares (company)			(10,936)			(10,936)
Dividends - common shares (NCI)							(157)
Dividends - common shares (total)	(11,093)
Other comprehensive income (loss)	480			287		287	193
Acquisitions, at cost (company)					$ (421)	(421)
Acquisitions, at cost (NCI)							(245)
Acquisitions, at cost (total)	$ (666)
Acquisitions (in shares)	(6)				(6)
Dispositions	$ 4				$ 4	4
Balance at Sep. 30, 2019	$ 197,109	15,795	419,367	(19,277)	(225,970)	189,915	7,194
Balance (in shares) - issued at Sep. 30, 2019	8,019
Balance (in shares) - in treasury at Sep. 30, 2019	(3,788)
Balance (in shares) - outstanding at Sep. 30, 2019	4,231
Balance at Jun. 30, 2019	$ 198,465	15,639	419,913	(18,205)	(225,970)	191,377	7,088
Balance (in shares) - issued at Jun. 30, 2019	8,019
Balance (in shares) - in treasury at Jun. 30, 2019	(3,788)
Balance (in shares) - outstanding at Jun. 30, 2019	4,231
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amortization of stock-based awards	$ 156	156				156
Other	228						228
Net income (loss) for the period	3,247		3,170			3,170	77
Dividends - common shares (company)			(3,716)			(3,716)
Dividends - common shares (NCI)							(57)
Dividends - common shares (total)	(3,773)
Other comprehensive income (loss)	(1,135)			(1,072)		(1,072)	(63)
Acquisitions, at cost (NCI)							(79)
Acquisitions, at cost (total)	(79)
Balance at Sep. 30, 2019	$ 197,109	15,795	419,367	(19,277)	(225,970)	189,915	7,194
Balance (in shares) - issued at Sep. 30, 2019	8,019
Balance (in shares) - in treasury at Sep. 30, 2019	(3,788)
Balance (in shares) - outstanding at Sep. 30, 2019	4,231
Balance at Dec. 31, 2019	$ 198,938	15,637	421,341	(19,493)	(225,835)	191,650	7,288
Balance (in shares) - issued at Dec. 31, 2019	8,019
Balance (in shares) - in treasury at Dec. 31, 2019	(3,785)
Balance (in shares) - outstanding at Dec. 31, 2019	4,234
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amortization of stock-based awards	$ 545	545				545
Other	389	(185)				(185)	574
Net income (loss) for the period	(2,648)		(2,370)			(2,370)	(278)
Dividends - common shares (company)			(11,150)			(11,150)
Dividends - common shares (NCI)							(137)
Dividends - common shares (total)	(11,287)
Cumulative effect of accounting change	(94)		(93)			(93)	(1)
Other comprehensive income (loss)	(867)			(696)		(696)	(171)
Acquisitions, at cost (company)					$ (305)	(305)
Acquisitions, at cost (NCI)							(63)
Acquisitions, at cost (total)	$ (368)
Acquisitions (in shares)	(6)				(6)
Dispositions	$ 4				$ 4	4
Balance at Sep. 30, 2020	$ 184,612	15,997	407,728	(20,189)	(226,136)	177,400	7,212
Balance (in shares) - issued at Sep. 30, 2020	8,019
Balance (in shares) - in treasury at Sep. 30, 2020	(3,791)
Balance (in shares) - outstanding at Sep. 30, 2020	4,228
Balance at Jun. 30, 2020	$ 187,153	15,812	412,124	(21,617)	(226,136)	180,183	6,970
Balance (in shares) - issued at Jun. 30, 2020	8,019
Balance (in shares) - in treasury at Jun. 30, 2020	(3,791)
Balance (in shares) - outstanding at Jun. 30, 2020	4,228
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amortization of stock-based awards	$ 187	187				187
Other	192	(2)				(2)	194
Net income (loss) for the period	(709)		(680)			(680)	(29)
Dividends - common shares (company)			(3,716)			(3,716)
Dividends - common shares (NCI)							(44)
Dividends - common shares (total)	(3,760)
Other comprehensive income (loss)	1,549			1,428		1,428	121
Balance at Sep. 30, 2020	$ 184,612	$ 15,997	$ 407,728	$ (20,189)	$ (226,136)	$ 177,400	$ 7,212
Balance (in shares) - issued at Sep. 30, 2020	8,019
Balance (in shares) - in treasury at Sep. 30, 2020	(3,791)
Balance (in shares) - outstanding at Sep. 30, 2020	4,228