Global Health Care Medical Costs Payable - Activity (Details) - Accident and health insurance [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Medical Claims Payable Activity [Abstract]
Costs payable, beginning balance, gross	$ 2,180	$ 2,050	$ 1,856
Less: Reinsurance and other amounts recoverable	252	194	242
Balance at January 1, net	1,928	1,856	1,614
Incurred claims related to:
Current year	18,564	16,853	16,049
Prior years	(210)	(159)	(182)
Total incurred	18,354	16,694	15,867
Paid claims related to:
Current year	16,588	14,966	14,267
Prior years	1,582	1,656	1,358
Total paid	18,170	16,622	15,625
Ending balance, net	2,112	1,928	1,856
Add: Reinsurance and other amounts recoverable	243	252	194
Costs payable, ending balance, gross	$ 2,355	$ 2,180	$ 2,050