Reinsurance (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Property-liability insurance claims and claims expense
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ 131	$ 161
Life and annuity contract benefits
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	47	67
Interest credited to contractholder funds
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	5	5
Property-liability insurance premiums earned
Reductions to premiums and contract charges due to reinsurance premium ceded amounts
Property-liability insurance premiums earned	246	249
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	$ 74