Global Health Care Medical Costs Payable - Prior Year Development (Details) - Accident and health insurance [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Abstract]
(Favorable) Unfavorable incurred costs related to prior years' claims payable	$ (210)	$ (159)	$ (182)
Incurred costs related to prior years' claims payable percentage	1.30%	1.00%
Favorable (unfavorable) impact of prior development on shareholders' net income	$ 60	$ 53
Completion Factors [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Abstract]
(Favorable) Unfavorable incurred costs related to prior years' claims payable	$ (62)	$ (61)
Incurred costs related to prior years' claims payable percentage	0.40%	0.40%
Medical Cost Trend [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Abstract]
(Favorable) Unfavorable incurred costs related to prior years' claims payable	$ (115)	$ (98)
Incurred costs related to prior years' claims payable percentage	0.70%	0.60%
Reinsurance Reimbursements Under Health Care Reform [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Abstract]
(Favorable) Unfavorable incurred costs related to prior years' claims payable	$ (33)
Incurred costs related to prior years' claims payable percentage	0.20%