Significant Accounting Policies - Narrative (Details) people in Millions, patient in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021 USD ($) patient clinic people location state	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) Segment patient clinic people state location	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Significant Accounting Policies [Line Items]
Number of pharmacy plan members | people	110		110
Number of patients served per year | patient	1		1
Number of reportable segments | Segment			4
Health insurer fee	$ 0	$ 255,000,000	$ 0	$ 774,000,000
Payments to HIF					$ 1,000,000,000
Related party transaction, expenses from transactions with related party	16,000,000	5,000,000	35,000,000	28,000,000
Related party transaction, other revenues from transactions with related party	$ 20,000,000	$ 15,000,000	$ 57,000,000	$ 58,000,000
Heartland Healthcare Services
Significant Accounting Policies [Line Items]
Number of states in which entity operates | state	4		4
Retail/ LTC
Significant Accounting Policies [Line Items]
Number of stores | location	9,900		9,900
Number of walk in medical clinics | clinic	1,200		1,200
Health Care Benefits
Significant Accounting Policies [Line Items]
Number of people served | people	35		35
Individual Public Health Insurance Exchanges, Submitted Regulatory Filings, Number of States | state			8