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Pension And Other Postretirement Benefits (Summary Of The Change In Accumulated Other Comprehensive Income) (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]      
Total (charge)/credit to other comprehensive income, before tax $ (5,155) $ (167) $ 1,845
(Charge)/credit to income tax (see Note 18) 1,495 35 (591)
(Charge)/credit to investment in equity companies (30) 11 (133)
(Charge)/credit to other comprehensive income including noncontrolling interests, after tax (3,690) (121) 1,121
Charge/(credit) to equity of noncontrolling interests 288 95 93
(Charge)/credit to other comprehensive income attributable to ExxonMobil (3,402) (26) 1,214
Pension Benefits - U.S. [Member]
      
Defined Benefit Plan Disclosure [Line Items]      
Total (charge)/credit to other comprehensive income, before tax (1,438) 724 1,410
Pension Benefits - Non-U.S. [Member]
      
Defined Benefit Plan Disclosure [Line Items]      
Total (charge)/credit to other comprehensive income, before tax (3,446) (811) 85
Other Postretirement Benefits [Member]
      
Defined Benefit Plan Disclosure [Line Items]      
Total (charge)/credit to other comprehensive income, before tax $ (271) $ (80) $ 350