Supplemental Financial Information - Amounts Reclassified out of AOCI (Details) - Reclassification out of Accumulated Other Comprehensive Income - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |||||
|---|---|---|---|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
Jun. 30, 2018 |
Jun. 30, 2017 |
||||
| Net actuarial losses of defined benefit plans | |||||||
| Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items] | |||||||
| Reclassified from other comprehensive income (loss), before tax | [1] | $ 11 | $ 16 | $ 23 | $ 34 | ||
| Tax Effect | (2) | (5) | (5) | (11) | |||
| Recognized within Net income, net of taxes | 9 | 11 | 18 | 23 | |||
| Prior service credit of defined benefit plans | |||||||
| Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items] | |||||||
| Reclassified from other comprehensive income (loss), before tax | [1] | (1) | (2) | (2) | (3) | ||
| Tax Effect | 0 | 1 | 0 | 1 | |||
| Recognized within Net income, net of taxes | $ (1) | $ (1) | $ (2) | $ (2) | |||
| |||||||