Reinsurance (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Property-liability insurance claims and claims expense
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ 124	$ 241	$ 255	$ 402
Life and annuity contract benefits
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	70	80	117	147
Interest credited to contractholder funds
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	6	6	11	11
Property-liability insurance premiums earned
Reductions to premiums and contract charges due to reinsurance premium ceded amounts
Property-liability insurance premiums earned	254	248	500	497
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	$ 75	$ 78	$ 150	$ 152