| **Pension and Postretirement Benefit Plans and Defined Contribution Plans - Pension Plans in Excess of Plan Assets (Detail) - USD ($) $ in Millions** | Dec. 31, 2015 | Dec. 31, 2014 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| U.S. Qualified Pension Plans [Member]                                                                                                                 |          |          |
| **Pension plans with an accumulated benefit obligation in excess of plan assets:**                                                                    |          |          |
| Fair value of plan assets                                                                                                                             | $ 11,633      | $ 12,706      |
| Accumulated benefit obligation                                                                                                                        | 14,755        | 16,323        |
| **Pension plans with a projected benefit obligation in excess of plan assets:**                                                                       |          |          |
| Fair value of plan assets                                                                                                                             | 11,633        | 12,706        |
| Projected benefit obligation                                                                                                                          | 14,926        | 16,575        |
| U.S. Supplemental (Non-Qualified) Pension Plans [Member]                                                                                              |          |          |
| **Pension plans with an accumulated benefit obligation in excess of plan assets:**                                                                    |          |          |
| Accumulated benefit obligation                                                                                                                        | 1,324         | 1,447         |
| **Pension plans with a projected benefit obligation in excess of plan assets:**                                                                       |          |          |
| Projected benefit obligation                                                                                                                          | 1,343         | 1,481         |
| International Pension Plans [Member]                                                                                                                  |          |          |
| **Pension plans with an accumulated benefit obligation in excess of plan assets:**                                                                    |          |          |
| Fair value of plan assets                                                                                                                             | 976           | 1,718         |
| Accumulated benefit obligation                                                                                                                        | 2,495         | 4,021         |
| **Pension plans with a projected benefit obligation in excess of plan assets:**                                                                       |          |          |
| Fair value of plan assets                                                                                                                             | 1,546         | 1,999         |
| Projected benefit obligation                                                                                                                          | $ 3,373       | $ 4,715       |

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| - References
No definition available.
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| - Definition
If aggregate disclosures are presented, the aggregate pension accumulated benefit obligation for pension plans with accumulated benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=58242635&loc=d3e4179-114921Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2417-114920
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
If aggregate disclosures are presented, the aggregate fair value of plan assets for pension plans with accumulated benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=58242635&loc=d3e4179-114921Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2417-114920
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| X                                                                                                                                                                                                                                                   |
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| - References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
If aggregate disclosures are presented, the aggregate benefit obligation for plans with benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2417-114920
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
If aggregate disclosures are presented, the aggregate fair value of plan assets for plans with benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2417-114920
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