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Other Comprehensive Income (Loss) - Changes in AOCI by Component (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Jan. 01, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |
Beginning Balance | $ 34,569 | $ 40,308 | $ 44,767 |
Other comprehensive income (loss), net of taxes | (361) | 316 | (1,078) |
Adoption of ASU 2018-02 (see Note 2) | (266) |  |  |
Adoption of new accounting standards (see Note 2) | 48 |  |  |
Ending Balance | 26,882 | 34,569 | 40,308 |
Derivatives |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |
Beginning Balance | (108) | 338 | 404 |
Other comprehensive income (loss) before reclassification adjustments, pretax | 228 | (561) | 210 |
Tax | (55) | 207 | (72) |
Other comprehensive income (loss) before reclassification adjustments, net of taxes | 173 | (354) | 138 |
Reclassification adjustments, pretax | 157 | (141) | (314) |
Tax | (33) | 49 | 110 |
Reclassification adjustments, net of taxes | 124 | (92) | (204) |
Other comprehensive income (loss), net of taxes | 297 | (446) | (66) |
Adoption of ASU 2018-02 (see Note 2) | (23) |  |  |
Adoption of new accounting standards (see Note 2) |  |  |  | $ 0
Ending Balance | 166 | (108) | 338 |
Investments |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |
Beginning Balance | (61) | (3) | 41 |
Other comprehensive income (loss) before reclassification adjustments, pretax | (108) | 212 | (38) |
Tax | 1 | (35) | 16 |
Other comprehensive income (loss) before reclassification adjustments, net of taxes | (107) | 177 | (22) |
Reclassification adjustments, pretax | 97 | (291) | (31) |
Tax | 0 | 56 | 9 |
Reclassification adjustments, net of taxes | 97 | (235) | (22) |
Other comprehensive income (loss), net of taxes | (10) | (58) | (44) |
Adoption of ASU 2018-02 (see Note 2) | 1 |  |  |
Adoption of new accounting standards (see Note 2) |  |  |  | (8)
Ending Balance | (78) | (61) | (3) |
Employee Benefit Plans |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |
Beginning Balance | (2,787) | (3,206) | (2,407) |
Other comprehensive income (loss) before reclassification adjustments, pretax | (728) | 438 | (1,199) |
Tax | 169 | (106) | 363 |
Other comprehensive income (loss) before reclassification adjustments, net of taxes | (559) | 332 | (836) |
Reclassification adjustments, pretax | 170 | 117 | 37 |
Tax | (36) | (30) | 0 |
Reclassification adjustments, net of taxes | 134 | 87 | 37 |
Other comprehensive income (loss), net of taxes | (425) | 419 | (799) |
Adoption of ASU 2018-02 (see Note 2) | (344) |  |  |
Adoption of new accounting standards (see Note 2) |  |  |  | 0
Ending Balance | (3,556) | (2,787) | (3,206) |
Pension Plan Net Loss |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |
Pension and other postretirement benefit plans, net loss and prior service credit included in AOCI | 4,400 | 3,500 |  |
Other Postretirement Benefit Plan Net Loss |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |
Pension and other postretirement benefit plans, net loss and prior service credit included in AOCI | (170) | (16) |  |
Pension Plan Prior Service Credit |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |
Pension and other postretirement benefit plans, net loss and prior service credit included in AOCI | 314 | 326 |  |
Other Postretirement Benefit Plan Prior Service Credit |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |
Pension and other postretirement benefit plans, net loss and prior service credit included in AOCI | 375 | 383 |  |
Cumulative Translation Adjustment |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |
Beginning Balance | (1,954) | (2,355) | (2,186) |
Other comprehensive income (loss) before reclassification adjustments, pretax | (84) | 235 | (150) |
Tax | (139) | 166 | (19) |
Other comprehensive income (loss) before reclassification adjustments, net of taxes | (223) | 401 | (169) |
Reclassification adjustments, pretax | 0 | 0 | 0 |
Tax | 0 | 0 | 0 |
Reclassification adjustments, net of taxes | 0 | 0 | 0 |
Other comprehensive income (loss), net of taxes | (223) | 401 | (169) |
Adoption of ASU 2018-02 (see Note 2) | 100 |  |  |
Adoption of new accounting standards (see Note 2) |  |  |  | 0
Ending Balance | (2,077) | (1,954) | (2,355) |
Accumulated Other Comprehensive Income (Loss) |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |
Beginning Balance | (4,910) | (5,226) | (4,148) |
Other comprehensive income (loss) before reclassification adjustments, pretax | (692) | 324 | (1,177) |
Tax | (24) | 232 | 288 |
Other comprehensive income (loss) before reclassification adjustments, net of taxes | (716) | 556 | (889) |
Reclassification adjustments, pretax | 424 | (315) | (308) |
Tax | (69) | 75 | 119 |
Reclassification adjustments, net of taxes | 355 | (240) | (189) |
Other comprehensive income (loss), net of taxes | (361) | 316 | (1,078) |
Adoption of new accounting standards (see Note 2) |  |  |  | $ (8)
Ending Balance | $ (5,545) | $ (4,910) | $ (5,226) |

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