Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Allowance for doubtful accounts | |||
| SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] | |||
| Balance at Beginning of Period | $ 34 | $ 28 | $ 17 |
| Additions | 195 | 208 | 174 |
| Deductions | (195) | (202) | (163) |
| Balance at End of Period | 34 | 34 | 28 |
| Deferred tax asset valuation allowance | |||
| SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] | |||
| Balance at Beginning of Period | 1,294 | 1,074 | 882 |
| Additions | 8,616 | 227 | 192 |
| Deductions | (55) | (7) | 0 |
| Balance at End of Period | 9,855 | 1,294 | 1,074 |
| Insurance reserves | |||
| SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] | |||
| Balance at Beginning of Period | 2,937 | 1,996 | 712 |
| Additions | 1,451 | 1,578 | 1,687 |
| Deductions | (970) | (637) | (403) |
| Balance at End of Period | 3,418 | 2,937 | 1,996 |
| Increase (decrease) for changes in estimates | $ 9 | $ (74) | $ 318 |