Global Health Care Medical Costs Payable - Prior Year Development (Details) - Accident and health insurance [Member] - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Abstract]
(Favorable) Unfavorable incurred costs related to prior years' claims payable	$ (203)		$ (159)
Incurred costs related to prior years' claims payable percentage	1.20%		1.00%
Favorable (unfavorable) impact of prior development on shareholders' net income	$ 57	$ 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	$ (56)		$ (61)
Incurred costs related to prior years' claims payable percentage	0.30%		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	$ (114)		$ (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%