Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions |
Dec. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Current Assets: | ||
| Allowance for uncollectible accounts | $ 13 | $ 12 |
| Allowance for obsolescence | 82 | 102 |
| Noncurrent Assets: | ||
| Accumulated depreciation and amortization | 17,027 | 15,823 |
| Accumulated amortization | $ 873 | $ 862 |
| Stockholders' Equity: | ||
| Common stock, par value (usd per share) | $ 0.0001 | $ 0.0001 |
| Common stock, shares authorized (shares) | 1,500,000,000 | 1,500,000,000 |
| Common stock, shares issued (shares) | 651,731,443 | 688,136,306 |
| Treasury stock, at cost (shares) | 8,959,730 | 8,191,831 |