Reinsurance (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Property-liability insurance claims and claims expense
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ 493	$ 107	$ 895	$ 441
Life and annuity contract benefits
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	25	23	172	150
Interest credited to contractholder funds
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	7	6	18	19
Property-liability insurance premiums earned
Reductions to premiums and contract charges due to reinsurance premium ceded amounts
Property-liability insurance premiums earned	244	246	741	757
Life and annuity premiums and contract charges
Reductions to premiums and contract charges due to reinsurance premium ceded amounts
Life and annuity premiums and contract charges	$ 78	$ 82	$ 230	$ 252