Global Health Care Medical Costs Payable - Activity (Details) - Global Health Benefits Segment [Member] - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Medical Claims Payable Activity [Abstract]
Costs payable, beginning balance, gross	$ 2,355	$ 2,180
Less: Reinsurance and other amounts recoverable	243	252
Balance at January 1, net	2,112	1,928
Incurred claims related to:
Current year	14,318	18,564
Prior years	(88)	(210)
Total incurred	14,230	18,354
Paid claims related to:
Current year	12,285	16,588
Prior years	1,783	1,582
Total paid	14,068	18,170
Ending balance, net	2,274	2,112
Add: Reinsurance and other amounts recoverable	276	243
Costs payable, ending balance, gross	$ 2,550	$ 2,355