v3.3.1.900
Long-Term Debt (Summarized Long-Term Debt) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Debt Instrument, Unamortized Premium $ 179 $ 219
Long-term debt 19,925 11,653
Combined Exxon Mobil And Affiliates [Member] | Other U.S. Dollar Obligations [Member]    
Other long-term debt [1] $ 97 $ 104
Average effective interest rate 3.80% 4.20%
Combined Exxon Mobil And Affiliates [Member] | Other Foreign Currency Obligations [Member]    
Other long-term debt $ 1 $ 9
0.921% Notes Due 2017 [Member] | Exxon Mobil Corporation [Member] | Other U.S. Dollar Obligations [Member]    
Senior notes, noncurrent $ 1,500 $ 1,500
Interest rate 0.921% 0.921%
Debt maturity Mar. 15, 2017 Mar. 15, 2017
Floating-Rate Notes Due 2017 [Member] | Exxon Mobil Corporation [Member] | Other U.S. Dollar Obligations [Member]    
Senior notes, noncurrent [2] $ 750 $ 750
Debt maturity Mar. 15, 2017 Mar. 15, 2017
Average effective interest rate 0.30% 0.30%
Floating-Rate Notes Due 2018 [Member] | Exxon Mobil Corporation [Member] | Other U.S. Dollar Obligations [Member]    
Senior notes, noncurrent [3] $ 500  
Debt maturity Mar. 01, 2018  
Average effective interest rate 0.40%  
1.305% Notes Due 2018 [Member] | Exxon Mobil Corporation [Member] | Other U.S. Dollar Obligations [Member]    
Senior notes, noncurrent $ 1,600  
Interest rate 1.305%  
Debt maturity Mar. 06, 2018  
1.819% Notes Due 2019 [Member] | Exxon Mobil Corporation [Member] | Other U.S. Dollar Obligations [Member]    
Senior notes, noncurrent $ 1,750 $ 1,750
Interest rate 1.819% 1.819%
Debt maturity Mar. 15, 2019 Mar. 15, 2019
Floating-Rate Notes Due 2019 [Member] | Exxon Mobil Corporation [Member] | Other U.S. Dollar Obligations [Member]    
Senior notes, noncurrent [4] $ 500 $ 500
Debt maturity Mar. 15, 2019 Mar. 15, 2019
Average effective interest rate 0.50% 0.40%
1.912% Notes Due 2020 [Member] | Exxon Mobil Corporation [Member] | Other U.S. Dollar Obligations [Member]    
Senior notes, noncurrent $ 1,500  
Interest rate 1.912%  
Debt maturity Mar. 06, 2020  
2.397% Notes Due 2022 [Member] | Exxon Mobil Corporation [Member] | Other U.S. Dollar Obligations [Member]    
Senior notes, noncurrent $ 1,150  
Interest rate 2.397%  
Debt maturity Mar. 06, 2022  
Floating-Rate Notes Due 2022 [Member] | Exxon Mobil Corporation [Member] | Other U.S. Dollar Obligations [Member]    
Senior notes, noncurrent [5] $ 500  
Debt maturity Mar. 06, 2022  
Average effective interest rate 0.70%  
3.176% Notes Due 2024 [Member] | Exxon Mobil Corporation [Member] | Other U.S. Dollar Obligations [Member]    
Senior notes, noncurrent $ 1,000 $ 1,000
Interest rate 3.176% 3.176%
Debt maturity Mar. 15, 2024 Mar. 15, 2024
2.709% Notes Due 2025 [Member] | Exxon Mobil Corporation [Member] | Other U.S. Dollar Obligations [Member]    
Senior notes, noncurrent $ 1,750  
Interest rate 2.709%  
Debt maturity Mar. 06, 2025  
3.567% Notes Due 2045 [Member] | Exxon Mobil Corporation [Member] | Other U.S. Dollar Obligations [Member]    
Senior notes, noncurrent $ 1,000  
Interest rate 3.567%  
Debt maturity Mar. 06, 2045  
5.650% Senior Notes Due 2016 [Member] | XTO Energy Inc. [Member]    
Senior notes, noncurrent   $ 207
Interest rate   5.65%
Debt maturity   Apr. 01, 2016
6.250% Senior Notes Due 2017 [Member] | XTO Energy Inc. [Member]    
Senior notes, noncurrent $ 465 $ 477
Interest rate 6.25% 6.25%
Debt maturity Aug. 01, 2017 Aug. 01, 2017
5.500% Senior Notes Due 2018 [Member] | XTO Energy Inc. [Member]    
Senior notes, noncurrent $ 377 $ 383
Interest rate 5.50% 5.50%
Debt maturity Jun. 15, 2018 Jun. 15, 2018
6.500% Senior Notes Due 2018 [Member] | XTO Energy Inc. [Member]    
Senior notes, noncurrent $ 463 $ 474
Interest rate 6.50% 6.50%
Debt maturity Dec. 15, 2018 Dec. 15, 2018
6.100% Senior Notes Due 2036 [Member] | XTO Energy Inc. [Member]    
Senior notes, noncurrent $ 198 $ 199
Interest rate 6.10% 6.10%
Debt maturity Apr. 01, 2036 Apr. 01, 2036
6.750% Senior Notes Due 2037 [Member] | XTO Energy Inc. [Member]    
Senior notes, noncurrent $ 307 $ 309
Interest rate 6.75% 6.75%
Debt maturity Aug. 01, 2037 Aug. 01, 2037
6.375% Senior Notes Due 2038 [Member] | XTO Energy Inc. [Member]    
Senior notes, noncurrent $ 235 $ 236
Interest rate 6.375% 6.375%
Debt maturity Jun. 15, 2038 Jun. 15, 2038
Variable Notes Due 2016-2019 [Member] | Mobil Producing Nigeria Unlimited [Member]    
Senior notes, noncurrent [6] $ 101 $ 399
Debt Instrument, maturity date range, start Dec. 15, 2017 Jun. 15, 2016
Debt Instrument, maturity date range, end Mar. 15, 2019 Mar. 15, 2019
Average effective interest rate 4.60% 4.50%
Variable Notes Due 2016-2020 [Member] | Esso (Thailand) Public Company Ltd. [Member]    
Senior notes, noncurrent [7] $ 83 $ 121
Debt Instrument, maturity date range, start Nov. 30, 2017 Nov. 30, 2017
Debt Instrument, maturity date range, end May 10, 2020 Dec. 31, 2019
Average effective interest rate 2.10% 2.40%
Debentures Due 2021 [Member] | Mobil Corporation [Member]    
Other long-term debt $ 249 $ 249
Interest rate 8.625% 8.625%
Debt maturity Aug. 15, 2021 Aug. 15, 2021
Industrial Revenue Bonds Due 2017-2051 [Member] | Combined Exxon Mobil And Affiliates [Member]    
Other long-term debt [8] $ 2,611 $ 2,611
Debt Instrument, maturity date range, start Apr. 01, 2017 Apr. 01, 2017
Debt Instrument, maturity date range, end Dec. 01, 2051 Dec. 01, 2051
Average effective interest rate 0.02% 0.03%
Capitalized Lease Obligations [Member] | Combined Exxon Mobil And Affiliates [Member]    
Average effective interest rate 9.20% 7.00%
Long-term debt [9] $ 1,238 $ 375
[1] Average effective interest rate of 3.8% in 2015 and 4.2% in 2014.
[2] Average effective interest rate of 0.3% in 2015 and 0.3% in 2014.
[3] Average effective interest rate of 0.4% in 2015.
[4] Average effective interest rate of 0.5% in 2015 and 0.4% in 2014.
[5] Average effective interest rate of 0.7% in 2015.
[6] Average effective interest rate of 4.6% in 2015 and 4.5% in 2014.
[7] Average effective interest rate of 2.1% in 2015 and 2.4% in 2014.
[8] Average effective interest rate of 0.02% in 2015 and 0.03% in 2014.
[9] Average imputed interest rate of 9.2% in 2015 and 7.0% in 2014.