Global Health Care Medical Costs Payable (Details) - Global Health Benefits Segment [Member] - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Incurred but not reported	$ 1,858	$ 1,757
Reported claims in process	556	470
Phyician incentives and other medical care expense and services payable	118	128
Total liability for unpaid claims and claims expenses	$ 2,532	$ 2,355	$ 2,180	$ 2,050