Medical Claims and Benefits Payable - Components of the Change (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Medical claims and benefits payable, beginning balance	$ 1,961	$ 2,192	$ 1,929
Components of medical care costs related to:
Current period	14,176	15,478	17,037
Prior periods	(271)	(341)	36
Total medical care costs	13,905	15,137	17,073
Change in non-risk and other provider payables	24	13	(106)
Payments for medical care costs related to:
Current period	12,554	13,671	15,130
Prior periods	1,482	1,710	1,574
Total paid	14,036	15,381	16,704
Medical claims and benefits payable, ending balance	$ 1,854	1,961	$ 2,192
CMS Subsidies
Liability for Claims and Claims Adjustment Expense [Line Items]
Disposal group, operating expense		$ 81