Organization and Basis of Presentation (Details) member in Thousands, $ in Millions				1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 25, 2021 USD ($)	Oct. 07, 2021 USD ($)	Apr. 22, 2021 USD ($)	Sep. 30, 2021 member position	Sep. 30, 2021 USD ($) member position	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) member position	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) member	Aug. 31, 2021 position
Segment Reporting Information [Line Items]
Contract term				4 years
Net cash paid in business combinations							$ 0	$ 62
Premium revenue					$ 6,800	$ 4,768	$ 19,689	$ 13,444
Extension option				2 years
AgeWell New York | New York
Segment Reporting Information [Line Items]
Number of members covered | position										13,000
Premium revenue									$ 700
Cigna Corporation's Texas Medicaid and Medicare-Medicaid Plan
Segment Reporting Information [Line Items]
Premium revenue									$ 1,000
Cigna Corporation's Texas Medicaid and Medicare-Medicaid Plan | Hidalgo, Tarrant and Northeast Service Areas
Segment Reporting Information [Line Items]
Number of members covered | member									48
Cigna Corporation's Texas Medicaid and Medicare-Medicaid Plan | Hidalgo Service Area
Segment Reporting Information [Line Items]
Number of members covered | member									2
New York Acquisition—Medicaid | Subsequent event
Segment Reporting Information [Line Items]
Net cash paid in business combinations	$ 380
Total Purchase price		$ 110
Cigna Corporation's Texas Medicaid and Medicare-Medicaid Plan
Segment Reporting Information [Line Items]
Total Purchase price			$ 60
Health Plans
Segment Reporting Information [Line Items]
Number of members eligible for the health care programs, approximately | member				4,800	4,800		4,800
Number of states with programs | position				18	18		18
Minimum | Health Plans
Segment Reporting Information [Line Items]
Contract term							3 years
Maximum | Health Plans
Segment Reporting Information [Line Items]
Contract term							5 years