Investments and Cash - Internally Managed Portfolio (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]
Internally managed portfolio	$ 974	$ 931
internally managed portfolio [Member]
Schedule of Investments [Line Items]
Percentage of internally managed portfolio	9.00%	9.00%
Securities purchased for loss mitigation purposes [Member] | Obligations of state and political subdivisions
Schedule of Investments [Line Items]
Internally managed portfolio	30	28
Securities purchased for loss mitigation purposes [Member] | RMBS
Schedule of Investments [Line Items]
Internally managed portfolio	277	284
Securities purchased for loss mitigation purposes [Member] | Asset-backed securities
Schedule of Investments [Line Items]
Internally managed portfolio	133	127
Securities purchased for loss mitigation purposes [Member] | Other invested assets
Schedule of Investments [Line Items]
Internally managed portfolio	46	47
Other risk management strategies [Member] | Other invested assets
Schedule of Investments [Line Items]
Internally managed portfolio	83	35
Other risk management strategies [Member] | Fixed maturity securities
Schedule of Investments [Line Items]
Internally managed portfolio	401	322
Other Investment Strategies [Member] | Trading Securities [Member]
Schedule of Investments [Line Items]
Internally managed portfolio	$ 4	$ 88