Reinsurance (Reinsurance Recoverable by Category and Listing of Largest Reinsurers) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
2014	$ 12,349
Provision	357	390
% of Gross	2.90%
Largest reinsurers
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
2014	6,141
Provision	79
% of Gross	1.30%
Other reinsurers balances rated A- or better
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
2014	2,537
Provision	38
% of Gross	1.50%
Other reinsurers balances with ratings lower than A- or not rated
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
2014	501
Provision	94
% of Gross	18.80%
Other pools and government agencies
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
2014	324
Provision	11
% of Gross	3.40%
Structured settlements
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
2014	557
Provision	12
% of Gross	2.20%
Other captives
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
2014	1,986
Provision	23
% of Gross	1.20%
Other
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
2014	303
Provision	$ 100
% of Gross	33.00%