Global Health Care Medical Costs Payable (Details) - Global Health Benefits Segment [Member] - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Incurred but not yet reported	$ 1,947	$ 1,757
Reported claims in process	475	470
Phyician incentives and other medical expense payable	128	128
Medical costs payable	$ 2,550	$ 2,355	$ 2,180