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	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 1,851	$ 2,267	$ 1,751	$ 2,340
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	28	(8)	39	11
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	7	15	14	25
Purchases	378	490	789	806
Sales	(180)	(135)	(363)	(305)
Settlements	(164)	(146)	(259)	(312)
Transfers into Level 3	9	36	42	45
Transfers out of Level 3	(56)	(38)	(140)	(129)
Balance, Ending, Assets	1,873	2,481	1,873	2,481
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 recognized in net income (loss)	2	(15)		(18)
Fixed maturity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	1,648	2,036	1,507	2,092
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	8	(14)	16	1
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(12)	15	(2)	26
Purchases	359	486	747	775
Sales	(164)	(131)	(327)	(271)
Settlements	(145)	(121)	(196)	(280)
Transfers into Level 3	9	31	42	40
Transfers out of Level 3	(56)	(38)	(140)	(119)
Balance, Ending, Assets	1,647	2,264	1,647	2,264
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 recognized in net income (loss)		(18)		(18)
Corporate and other bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	486	577	482	624
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	3	(2)	6	2
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	2	2	6	(3)
Purchases	68	304	147	346
Sales	(27)	(30)	(113)	(50)
Settlements	(13)	(70)	(32)	(97)
Transfers into Level 3	9	31	42	40
Transfers out of Level 3	(40)		(50)	(50)
Balance, Ending, Assets	488	812	488	812
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 recognized in net income (loss)		(3)		(3)
States, municipalities and political subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	173	188	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	(1)	3
Purchases
Sales
Settlements	(85)	(8)	(85)	(87)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	89	179	89	179
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 recognized in net income (loss)
Asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	936	1,271	854	1,199
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	5	(12)	10	(4)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(15)	14	(11)	32
Purchases	291	182	547	429
Sales	(111)	(101)	(188)	(218)
Settlements	(47)	(43)	(79)	(96)
Transfers into Level 3
Transfers out of Level 3	(16)	(38)	(90)	(69)
Balance, Ending, Assets	1,043	1,273	1,043	1,273
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 recognized in net income (loss)		(15)		(15)
Residential mortgage-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	447	738	452	767
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	(13)	2	(12)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(18)	12	(22)	14
Purchases	22	50	60	97
Sales		(57)		(83)
Settlements	(9)	(19)	(16)	(41)
Transfers into Level 3
Transfers out of Level 3		(24)	(33)	(55)
Balance, Ending, Assets	443	687	443	687
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 recognized in net income (loss)		(15)		(15)
Commercial mortgage-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	105	88	59	73
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	2		2	3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	4	2	8	18
Purchases	87	5	129	5
Sales	(12)		(12)	(4)
Settlements	(4)		(4)
Transfers into Level 3
Transfers out of Level 3	(16)		(16)
Balance, Ending, Assets	166	95	166	95
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 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	384	445	343	359
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	2	1	6	5
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(1)		3
Purchases	182	127	358	327
Sales	(99)	(44)	(176)	(131)
Settlements	(34)	(24)	(59)	(55)
Transfers into Level 3
Transfers out of Level 3		(14)	(41)	(14)
Balance, Ending, Assets	434	491	434	491
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 recognized in net income (loss)
Redeemable preferred stock [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	53			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)				(3)
Purchases			53
Sales	(26)		(26)	(3)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	27		27
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 recognized in net income (loss)
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	74	30	67	26
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)		(1)		(2)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	19		16	(1)
Purchases	15	4	26	19
Sales	(15)	(2)	(16)	(11)
Settlements
Transfers into Level 3		5		5
Transfers out of Level 3
Balance, Ending, Assets	93	36	93	36
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 recognized in net income (loss)	(1)	(1)	(3)	(4)
Derivative and other financial instruments, net [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	10	8	10	25
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)		1		3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)
Purchases
Sales				(19)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	10	9	10	9
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 recognized in net income (loss)		1		1
Short term investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets		27	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	4		16	12
Sales
Settlements		(21)	(39)	(23)
Transfers into Level 3
Transfers out of Level 3				(10)
Balance, Ending, Assets	4	6	4	6
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 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	115	127	117	129
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	20	6	23	9
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)
Purchases
Sales
Settlements	(19)	(4)	(24)	(9)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	116	129	116	129
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 recognized in net income (loss)	3	3	3	3
Seperate account business [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	4	39	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	(1)	(2)	(20)	(4)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	3	37	3	37
Unrealized gains (losses) on Level 3 assets and liabilities held at June 30 recognized in net income (loss)