Global Health Care Medical Costs Payable - Activity (Details) - Global Health Benefits Segment [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 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	4,825	18,564
Prior years	(64)	(210)
Total incurred	4,761	18,354
Paid claims related to:
Current year	2,985	16,588
Prior years	1,449	1,582
Total paid	4,434	18,170
Ending balance, net	2,439	2,112
Add: Reinsurance and other amounts recoverable	207	243
Costs payable, ending balance, gross	$ 2,646	$ 2,355