Investments (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) securities	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) securities
Investment Narrative [Line Items]
Accounts Receivable, Allowance for Credit Loss	$ 2
Document Period End Date	Mar. 31, 2020
Impairment Losses On Securities Intended To Be Sold	$ 1
Allowance For Credit Losses Related To High Yield Securities	33
AOCI, Debt Securities, Available-for-sale with Allowance for Credit Loss, Cumulative Gain (Loss), after Tax	2	$ 4
Sales of fixed maturity securities available-for-sale	2,141	3,140
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Cash	5		$ 1
Available-for-sale Securities, Realized Losses, Excluding Other than Temporary Impairments	8	19
Available-for-sale Securities, Gross Realized Gains	$ 27	28
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities	3,102		1,072
Securities As Percentage Of Consolidated Stockholder Equity	10.00%
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%		100.00%
Funds withheld at interest	$ 5,258		$ 5,662
Funds Held Under Reinsurance Agreements Asset Specific Client	3,200
Gain (Loss) on Sale of Equity Investments	$ (23)	$ 4
CALIFORNIA
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	15.20%
TEXAS
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	14.70%
GEORGIA
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	8.70%
CANADA
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	2.90%
UNITED KINGDOM
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	0.90%