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Postretirement benefits Schedule of net periodic benefit costs (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract] |  |  |
Total (increase) decrease in other comprehensive (Income) Loss | $ 321 | $ 16 | $ (545)
Pension Plan [Member] |  |  |
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract] |  |  |
Service Cost | 69 | 80 | 93
Defined Benefit Plan, Non Service (Benefit) Cost | (124) | (123) | (188)
Net Periodic Benefit Cost | (55) | (43) | (95)
Pension Plan [Member] | UNITED STATES |  |  |
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract] |  |  |
Service Cost | 57 | 63 | 75
Interest Cost | 105 | 105 | 103
Expected Return on Plan Assets | (212) | (189) | (165)
Amortization of (Gains) Losses | 0 | 0 | 0
Amortization of Prior Service Cost (Credit) | 0 | 0 | 0
Recognized Net (Gain) Loss Due to Curtailments | 0 | 0 | (117)
Recognized Net (Gain) Loss Due to Settlements | 2 | 0 | (2)
Defined Benefit Plan, Non Service (Benefit) Cost | (105) | (84) | (181)
Net Periodic Benefit Cost | (48) | (21) | (106)
(Increase) decrease in Other Comprehensive Income (Loss), Net Actuarial (Gain) Loss) | 214 | (21) | (326)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), before Tax | 0 | 0 | 0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax | 0 | 0 | 0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax | 0 | 0 | 0
(Increase) decrease in other comprehensive income, curtailment | 0 | 0 | 117
(Increase) decrease in other comprehensive income, settlement | (2) | 1 | 2
Total (increase) decrease in other comprehensive (Income) Loss | 212 | (20) | (207)
Pension Plan [Member] | Non-US [Member] |  |  |
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract] |  |  |
Service Cost | 12 | 17 | 18
Interest Cost | 27 | 27 | 30
Expected Return on Plan Assets | (50) | (42) | (39)
Amortization of (Gains) Losses | 1 | 3 | 2
Amortization of Prior Service Cost (Credit) | 0 | 0 | (1)
Recognized Net (Gain) Loss Due to Curtailments | 0 | (27) | 0
Recognized Net (Gain) Loss Due to Settlements | 3 | 0 | 1
Defined Benefit Plan, Non Service (Benefit) Cost | (19) | (39) | (7)
Net Periodic Benefit Cost | (7) | (22) | 11
(Increase) decrease in Other Comprehensive Income (Loss), Net Actuarial (Gain) Loss) | 34 | (57) | 49
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), before Tax | 3 | 0 | (8)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax | (1) | (3) | 0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax | 0 | 0 | 0
(Increase) decrease in other comprehensive income, curtailment | 0 | (6) | 0
(Increase) decrease in other comprehensive income, settlement | (3) | 0 | (1)
Total (increase) decrease in other comprehensive (Income) Loss | 33 | (66) | 40
Other Postretirement Benefits Plan [Member] |  |  |
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract] |  |  |
Service Cost | 1 | 2 | 10
Interest Cost | 3 | 4 | 17
Expected Return on Plan Assets | (5) | (5) | (8)
Amortization of (Gains) Losses | 0 | 0 | (1)
Amortization of Prior Service Cost (Credit) | (85) | (89) | (15)
Recognized Net (Gain) Loss Due to Curtailments | (2) | (37) | 0
Recognized Net (Gain) Loss Due to Settlements | 0 | 0 | 0
Defined Benefit Plan, Non Service (Benefit) Cost | (89) | (127) | (7)
Net Periodic Benefit Cost | (88) | (125) | 3
(Increase) decrease in Other Comprehensive Income (Loss), Net Actuarial (Gain) Loss) | (11) | (3) | 17
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), before Tax | 0 | (23) | (395)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax | (1) | 0 | 0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax | 85 | 89 | 0
(Increase) decrease in other comprehensive income, curtailment | 3 | 39 | 0
(Increase) decrease in other comprehensive income, settlement | 0 | 0 | 0
Total (increase) decrease in other comprehensive (Income) Loss | 76 | 102 | (378)
Losses and loss expenses [Member] | Pension Plan [Member] |  |  |
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract] |  |  |
Service Cost | 7 | 7 | 8
Defined Benefit Plan, Non Service (Benefit) Cost | (10) | (8) | (18)
Losses and loss expenses [Member] | Other Postretirement Benefits Plan [Member] |  |  |
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract] |  |  |
Service Cost | 0 | 0 | 0
Defined Benefit Plan, Non Service (Benefit) Cost | (9) | (13) | 0
General and Administrative Expense [Member] | Pension Plan [Member] |  |  |
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract] |  |  |
Service Cost | 62 | 73 | 85
Defined Benefit Plan, Non Service (Benefit) Cost | (114) | (115) | (170)
General and Administrative Expense [Member] | Other Postretirement Benefits Plan [Member] |  |  |
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract] |  |  |
Service Cost | 1 | 2 | 10
Defined Benefit Plan, Non Service (Benefit) Cost | $ (80) | $ (114) | $ (7)

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