Claim And Claim Adjustment Expense Reserves (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Claim And Claim Adjustment Expense Reserves [Line Items]
Catastrophe losses net of reinsurance	$ 222,000,000	$ 121,000,000	$ 89,000,000
A&EP Reserves [Member]
Claim And Claim Adjustment Expense Reserves [Line Items]
Net A&EP claim and allocated claim adjustment expense reserves		1,600,000,000
Net A&EP claim and allocated claim adjustment expense reserves in discontinued operations		90,000,000
Ceded A&EP claim and allocated claim adjustment expense reserves		1,200,000,000
Reinsurance premium paid to NICO under A&EP Loss Portfolio Transfer		2,000,000,000
Net reinsurance receivables transferred to NICO under A&EP Loss Portfolio Transfer		215,000,000
Allowance for uncollectible reinsurance receivables		100,000,000
Collateral trust established by NICO under A&EP Loss Portfolio Transfer		2,200,000,000
Reduction of allowance collateral trust established by NICO under A&EP Loss Portfolio Transfer		200,000,000
Aggregate limit under A&EP Loss Portfolio Transfer		4,000,000,000
Gross Claim Adjustment Reserves Ceded	2,300,000,000	2,500,000,000
Adverse prior year development	138,000,000
Aggregate Limit Remaining	2,300,000,000
Net ultimate losses ceded under the Loss Portfolio Transfer	351,000,000
Life And Group Non-Core [Member]
Claim And Claim Adjustment Expense Reserves [Line Items]
Favorable Net Prior Year Development	29,000,000	2,000,000	53,000,000
Loss Recovery Gross			130,000,000
Loss Recovery Net			$ 94,000,000