Medical Costs Payable (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Medical costs payable, beginning of period	$ 21,690	$ 19,891
Acquisitions	41	522
Reported medical costs:
Current year	76,338	78,523
Prior year	(660)	(400)
Total reported medical costs	75,678	78,123
Medical payments:
Payments for current year	(59,482)	(60,707)
Payments for prior years	(18,727)	(16,922)
Total medical payments	(78,209)	(77,629)
Medical costs payable, end of period	$ 19,200	$ 20,907