GOODWILL AND OTHER INTANGIBLE ASSETS - Other Intangible Assets Subject to Amortization (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Other intangible assets:
Weighted average life (in years)	9 years 1 month 6 days
Total other intangible assets, cost	$ 3,444	$ 1,069
Amortizable intangible assets, accumulated amortization	786	740
Total other intangible assets, net	2,658	329
Certificates of need
Other intangible assets:
Indefinite-lived intangible assets	1,786	0
Medicare licenses
Other intangible assets:
Indefinite-lived intangible assets	$ 522	0
Customer contracts/ relationships
Other intangible assets:
Weighted average life (in years)	9 years 4 months 24 days
Amortizable intangible assets, cost	$ 876	849
Amortizable intangible assets, accumulated amortization	608	572
Amortizable intangible assets, net	$ 268	277
Trade names and technology
Other intangible assets:
Weighted average life (in years)	7 years 1 month 6 days
Amortizable intangible assets, cost	$ 156	122
Amortizable intangible assets, accumulated amortization	94	89
Amortizable intangible assets, net	$ 62	33
Provider contracts
Other intangible assets:
Weighted average life (in years)	11 years 8 months 12 days
Amortizable intangible assets, cost	$ 70	69
Amortizable intangible assets, accumulated amortization	55	50
Amortizable intangible assets, net	$ 15	19
Noncompetes and other
Other intangible assets:
Weighted average life (in years)	7 years
Amortizable intangible assets, cost	$ 34	29
Amortizable intangible assets, accumulated amortization	29	29
Amortizable intangible assets, net	$ 5	$ 0