Global Health Care Medical Costs Payable (Details) - Global Health Benefits Segment [Member] - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Incurred but not yet reported	$ 1,960	$ 1,757
Reported claims in process	506	470
Phyician incentives and other medical expense payable	180	128
Medical costs payable	$ 2,646	$ 2,355	$ 2,180