Medical Costs Payable Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Medical costs payable, beginning of period	$ 21,872	$ 21,690	$ 19,891
Acquisitions	88	316	679
Reported medical costs:
Current year	188,631	160,276	157,020
Prior years	(1,720)	(880)	(580)
Total reported medical costs	186,911	159,396	156,440
Medical payments:
Payments for current year	(165,524)	(139,974)	(137,155)
Payments for prior years	(18,864)	(19,556)	(18,165)
Total medical payments	(184,388)	(159,530)	(155,320)
Medical costs payable, end of period	$ 24,483	$ 21,872	$ 21,690