Fair Value (Table of reconciliation for assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 1,751	$ 2,340
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	28	21
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	33	(16)
Purchases	1,225	1,436
Sales	(580)	(917)
Settlements	(494)	(474)
Transfers into Level 3	59	86
Transfers out of Level 3	(629)	(725)
Balance, Ending, Assets	1,393	1,751
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	48	19
Fixed maturity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	1,507	2,092
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	11	(13)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	27	(18)
Purchases	1,175	1,330
Sales	(539)	(865)
Settlements	(373)	(400)
Transfers into Level 3	58	81
Transfers out of Level 3	(615)	(700)
Balance, Ending, Assets	1,251	1,507
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(21)	23
Corporate and other bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	482	624
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	6	(11)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	4	(1)
Purchases	231	484
Sales	(136)	(204)
Settlements	(88)	(149)
Transfers into Level 3	45	79
Transfers out of Level 3	(325)	(340)
Balance, Ending, Assets	219	482
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(3)	12
States, municipalities and political subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	171	266
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)		(1)
Purchases	14	3
Sales
Settlements	(89)	(92)
Transfers into Level 3
Transfers out of Level 3		(5)
Balance, Ending, Assets	96	171
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)
Residential mortgage-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	452	767
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(14)	(16)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	2	(11)
Purchases	97	225
Sales		(290)
Settlements	(40)	(60)
Transfers into Level 3
Transfers out of Level 3	(84)	(163)
Balance, Ending, Assets	413	452
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(18)	6
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	59	73
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	8	20
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	14	(7)
Purchases	165	81
Sales	(12)	(27)
Settlements	(28)
Transfers into Level 3	13
Transfers out of Level 3	(90)	(81)
Balance, Ending, Assets	129	59
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)
Other asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	343	359
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	11	(9)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	8	5
Purchases	615	537
Sales	(365)	(341)
Settlements	(128)	(99)
Transfers into Level 3		2
Transfers out of Level 3	(116)	(111)
Balance, Ending, Assets	368	343
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)		5
Total asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	854	1,199
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	5	(5)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	24	(13)
Purchases	877	843
Sales	(377)	(658)
Settlements	(196)	(159)
Transfers into Level 3	13	2
Transfers out of Level 3	(290)	(355)
Balance, Ending, Assets	910	854
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(18)	11
Redeemable Preferred Stock [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets		3
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)		3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(1)	(3)
Purchases	53
Sales	(26)	(3)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	26
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	67	26
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(36)	(2)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	6	2
Purchases	27	66
Sales	(16)	(27)
Settlements
Transfers into Level 3		5
Transfers out of Level 3	(14)	(3)
Balance, Ending, Assets	34	67
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(38)	3
Other invested assets, including derivatives, net
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	10	25
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)		3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)
Purchases		1
Sales		(19)
Settlements	(10)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets		10
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)		(2)
Short-term Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	27	27
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)
Purchases	23	39
Sales	(4)
Settlements	(41)	(29)
Transfers into Level 3	1
Transfers out of Level 3		(10)
Balance, Ending, Assets	6	27
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)
Life settlement contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	117	129
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	53	33
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)
Purchases
Sales
Settlements	(70)	(45)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	100	117
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	11	(5)
Separate account business [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	23	41
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)
Purchases
Sales	(21)	(6)
Settlements
Transfers into Level 3
Transfers out of Level 3		(12)
Balance, Ending, Assets	2	23
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)