Amounts Associated With 3Rs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Dec. 31, 2015
Supplementary Insurance Information, by Segment [Line Items]
Provision for premium deficiency	$ 176		$ 189	$ 176
Premium Deficiency Reserve Activity [Roll Forward]
Balance at January 1, 2016	189
Current period results applied to the PDR liability	13
Balance at March 31, 2016	176
Other current assets			17,844	15,711
Trade accounts payable and accrued expenses			(4,074)	(2,212)
Other long-term assets			2,465	2,475
Other long-term liabilities			(278)	(235)
Risk Adjustment Settlement
Premium Deficiency Reserve Activity [Roll Forward]
Total net (liability) asset			(134)	(87)
Reinsurance Recoverables
Premium Deficiency Reserve Activity [Roll Forward]
Total net (liability) asset			427	610
Risk Corridor Settlement
Premium Deficiency Reserve Activity [Roll Forward]
Total net (liability) asset			466	459
Health Care Reform
Premium Deficiency Reserve Activity [Roll Forward]
Payment of annual health insurance industry fee	908
Amortization of deferred charges	227	$ 220
2016 Coverage Year
Supplementary Insurance Information, by Segment [Line Items]
Provision for premium deficiency	176			176
Premium Deficiency Reserve Activity [Roll Forward]
Balance at March 31, 2016	176
2016 Coverage Year | Risk Adjustment Settlement
Premium Deficiency Reserve Activity [Roll Forward]
Other long-term assets			0	0
Other long-term liabilities			(12)	0
Net long-term asset			(12)	0
Total net (liability) asset			(12)	0
2016 Coverage Year | Reinsurance Recoverables
Premium Deficiency Reserve Activity [Roll Forward]
Other long-term assets			25	0
Other long-term liabilities			0	0
Net long-term asset			25	0
Total net (liability) asset			25	0
2016 Coverage Year | Risk Corridor Settlement
Premium Deficiency Reserve Activity [Roll Forward]
Other long-term assets			97	0
Other long-term liabilities			0	0
Net long-term asset			97	0
Total net (liability) asset			97	0
Current Coverage Year
Premium Deficiency Reserve Activity [Roll Forward]
Proceeds from reinsurance recoverable	213
Current Coverage Year | Risk Adjustment Settlement
Premium Deficiency Reserve Activity [Roll Forward]
Premiums receivable			136	126
Other current assets			0	0
Trade accounts payable and accrued expenses			(258)	(223)
Net current (liability) asset			(122)	(97)
Other long-term assets			0	10
Other long-term liabilities			0	0
Net long-term asset			0	10
Total net (liability) asset			(122)	(87)
Current Coverage Year | Reinsurance Recoverables
Premium Deficiency Reserve Activity [Roll Forward]
Premiums receivable			0	0
Other current assets			402	610
Trade accounts payable and accrued expenses			0	0
Net current (liability) asset			402	610
Other long-term assets			0	0
Other long-term liabilities			0	0
Net long-term asset			0	0
Total net (liability) asset			402	610
Current Coverage Year | Risk Corridor Settlement
Premium Deficiency Reserve Activity [Roll Forward]
Premiums receivable			0	0
Other current assets			0	0
Trade accounts payable and accrued expenses			0	0
Net current (liability) asset			0	0
Other long-term assets			369	459
Other long-term liabilities			0	0
Net long-term asset			369	459
Total net (liability) asset			$ 369	$ 459
2014 Coverage Year | Risk Corridor Settlement
Premium Deficiency Reserve Activity [Roll Forward]
Proceeds from risk corridor settlements	$ 30
Percent of receivable to be paid by CMS (between December 2015 and January 2016)			12.60%