SEGMENT INFORMATION - Narrative (Details) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2019
USD ($)
Segment
|
Dec. 31, 2018
USD ($)
|
Dec. 31, 2017
USD ($)
|
|
| Segment Reporting Information [Line Items] | |||
| Number of reportable segments | Segment | 3 | ||
| Member co-share amounts and government subsidies | $ 14,900 | $ 13,400 | $ 13,500 |
| Depreciation and amortization classified as benefit expense | $ 117 | $ 129 | $ 107 |
| Government Contracts Concentration Risk | Premiums and services revenue | Federal government contracts | |||
| Segment Reporting Information [Line Items] | |||
| Premiums and services revenue (percent) | 82.00% | 81.00% | 79.00% |