GOODWILL AND OTHER INTANGIBLE ASSETS - Changes in Carrying Amount of Goodwill by Reportable Segments (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Goodwill [Roll Forward] | ||
| Beginning balance | $ 3,897 | $ 3,281 |
| Acquisitions | 31 | 616 |
| Ending balance | 3,928 | 3,897 |
| Retail | ||
| Goodwill [Roll Forward] | ||
| Beginning balance | 1,535 | 1,059 |
| Acquisitions | 0 | 476 |
| Ending balance | 1,535 | 1,535 |
| Group and Specialty | ||
| Goodwill [Roll Forward] | ||
| Beginning balance | 261 | 261 |
| Acquisitions | 0 | 0 |
| Ending balance | 261 | 261 |
| Healthcare Services | ||
| Goodwill [Roll Forward] | ||
| Beginning balance | 2,101 | 1,961 |
| Acquisitions | 31 | 140 |
| Ending balance | $ 2,132 | $ 2,101 |