Condensed Consolidated Statement Of Changes In Equity (USD $) In Millions	Total USD ($)	Exxon Mobil Share Of Common Stock [Member] USD ($)	Exxon Mobil Share Of Earnings Reinvested [Member] USD ($)	Exxon Mobil Share Of Accumulated Other Comprehensive Income [Member] USD ($)	Exxon Mobil Share Of Common Stock Held In Treasury [Member] USD ($)	Exxon Mobil Share Of Equity [Member] USD ($)	Noncontrolling Interests [Member] USD ($)	Common Stock Outstanding [Member]
Balance at Dec. 31, 2013	$ 180,495	$ 10,077	$ 387,432	$ (10,725)	$ (212,781)	$ 174,003	$ 6,492
Balance (in shares) - outstanding at Dec. 31, 2013								4,335
Balance (in shares) - in treasury at Dec. 31, 2013					(3,684)
Balance (in shares) - issued at Dec. 31, 2013		8,019
Amortization of stock-based awards	201	201				201
Tax benefits related to stock-based awards	3	3				3
Other	(5)	(5)				(5)
Net income for the period	9,370		9,100			9,100	270
Dividends - common shares (company)			(2,732)			(2,732)
Dividends - common shares (NCI)							(58)
Dividends - common shares (total)	(2,790)
Other comprehensive income	(526)			(315)		(315)	(211)
Acquisitions, at cost (company)					(3,860)	(3,860)
Acquisitions, at cost (total)	(3,860)
Acquisitions (in shares)					(41)			(41)
Dispositions	3				3	3
Balance at Mar. 31, 2014	182,891	10,276	393,800	(11,040)	(216,638)	176,398	6,493
Balance (in shares) - outstanding at Mar. 31, 2014								4,294
Balance (in shares) - in treasury at Mar. 31, 2014					(3,725)
Balance (in shares) - issued at Mar. 31, 2014		8,019
Balance at Dec. 31, 2014	181,064	10,792	408,384	(18,957)	(225,820)	174,399	6,665
Balance (in shares) - outstanding at Dec. 31, 2014								4,201
Balance (in shares) - in treasury at Dec. 31, 2014	3,818				(3,818)
Balance (in shares) - issued at Dec. 31, 2014	8,019	8,019
Amortization of stock-based awards	213	213				213
Tax benefits related to stock-based awards	3	3				3
Other	(2)	(2)				(2)
Net income for the period	5,075		4,940			4,940	135
Dividends - common shares (company)			(2,910)			(2,910)
Dividends - common shares (NCI)							(40)
Dividends - common shares (total)	(2,950)
Other comprehensive income	(4,179)			(3,638)		(3,638)	(541)
Acquisitions, at cost (company)					(1,781)	(1,781)
Acquisitions, at cost (total)	(1,781)
Acquisitions (in shares)					(20)			(20)
Dispositions	3				3	3
Balance at Mar. 31, 2015	$ 177,446	$ 11,006	$ 410,414	$ (22,595)	$ (227,598)	$ 171,227	$ 6,219
Balance (in shares) - outstanding at Mar. 31, 2015								4,181
Balance (in shares) - in treasury at Mar. 31, 2015	3,838				(3,838)
Balance (in shares) - issued at Mar. 31, 2015	8,019	8,019