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		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 1,873	$ 2,481	$ 1,751	$ 2,340
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(22)	(1)	17	10
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	16	(21)	30	4
Purchases	233	380	1,022	1,186
Sales	(126)	(296)	(489)	(601)
Settlements	(80)	(100)	(339)	(412)
Transfers into Level 3	12	14	54	59
Transfers out of Level 3	(423)	(230)	(563)	(359)
Balance, Ending, Assets	1,483	2,227	1,483	2,227
Unrealized gains (losses) on Level 3 assets and liabilities held at Balance Sheet date recognized in net income (loss)	(38)	(15)	(37)	(30)
Fixed maturity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	1,647	2,264	1,507	2,092
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(10)	(11)	6	(10)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	26	(21)	24	5
Purchases	226	379	973	1,154
Sales	(122)	(293)	(449)	(564)
Settlements	(70)	(85)	(266)	(365)
Transfers into Level 3	11	14	53	54
Transfers out of Level 3	(409)	(227)	(549)	(346)
Balance, Ending, Assets	1,299	2,020	1,299	2,020
Unrealized gains (losses) on Level 3 assets and liabilities held at Balance Sheet date recognized in net income (loss)	(19)	(14)	(19)	(30)
Corporate and other bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	488	812	482	624
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	(7)	7	(5)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(4)	(3)	2	(6)
Purchases	50	113	197	459
Sales	(5)	(107)	(118)	(157)
Settlements	(11)	(47)	(43)	(144)
Transfers into Level 3		12	42	52
Transfers out of Level 3	(260)	(154)	(310)	(204)
Balance, Ending, Assets	259	619	259	619
Unrealized gains (losses) on Level 3 assets and liabilities held at Balance Sheet date recognized in net income (loss)	(1)	(10)	(1)	(11)
States, municipalities and political subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	89	179	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)			3
Purchases		3		3
Sales
Settlements			(85)	(87)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	89	182	89	182
Unrealized gains (losses) on Level 3 assets and liabilities held at Balance Sheet date recognized in net income (loss)
Asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	1,043	1,273	854	1,199
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(11)	(4)	(1)	(8)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	31	(18)	20	14
Purchases	176	263	723	692
Sales	(117)	(186)	(305)	(404)
Settlements	(59)	(38)	(138)	(134)
Transfers into Level 3	11	2	11	2
Transfers out of Level 3	(149)	(73)	(239)	(142)
Balance, Ending, Assets	925	1,219	925	1,219
Unrealized gains (losses) on Level 3 assets and liabilities held at Balance Sheet date recognized in net income (loss)	(18)	(4)	(18)	(19)
Residential mortgage-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	443	687	452	767
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(17)	1	(15)	(11)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	20	(5)	(2)	9
Purchases	21	73	81	170
Sales		(81)		(164)
Settlements	(8)	(13)	(24)	(54)
Transfers into Level 3
Transfers out of Level 3	(22)	(31)	(55)	(86)
Balance, Ending, Assets	437	631	437	631
Unrealized gains (losses) on Level 3 assets and liabilities held at Balance Sheet date recognized in net income (loss)	(18)		(18)	(15)
Commercial mortgage-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	166	95	59	73
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	4		6	3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	6	(7)	14	11
Purchases	12	76	141	81
Sales			(12)	(4)
Settlements	(17)		(21)
Transfers into Level 3	11		11
Transfers out of Level 3	(65)	(5)	(81)	(5)
Balance, Ending, Assets	117	159	117	159
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	434	491	343	359
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	2	(5)	8
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	5	(6)	8	(6)
Purchases	143	114	501	441
Sales	(117)	(105)	(293)	(236)
Settlements	(34)	(25)	(93)	(80)
Transfers into Level 3		2		2
Transfers out of Level 3	(62)	(37)	(103)	(51)
Balance, Ending, Assets	371	429	371	429
Unrealized gains (losses) on Level 3 assets and liabilities held at Balance Sheet date recognized in net income (loss)		(4)		(4)
Redeemable preferred stock [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	27			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)		(1)	(3)
Purchases			53
Sales			(26)	(3)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	26		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	93	36	67	26
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(19)		(19)	(2)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(10)		6	(1)
Purchases			26	19
Sales		(1)	(16)	(12)
Settlements
Transfers into Level 3				5
Transfers out of Level 3	(14)	(3)	(14)	(3)
Balance, Ending, Assets	50	32	50	32
Unrealized gains (losses) on Level 3 assets and liabilities held at Balance Sheet date recognized in net income (loss)	(19)		(21)	(3)
Derivative and other financial instruments, net [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	10	9	10	25
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)
Purchases		1		1
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 Balance Sheet date recognized in net income (loss)				1
Short term investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	4	6	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	7		23	12
Sales	(4)		(4)
Settlements			(39)	(23)
Transfers into Level 3	1		1
Transfers out of Level 3				(10)
Balance, Ending, Assets	8	6	8	6
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	116	129	117	129
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	7	11	30	20
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)
Purchases
Sales
Settlements	(10)	(15)	(34)	(24)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	113	125	113	125
Unrealized gains (losses) on Level 3 assets and liabilities held at Balance Sheet date recognized in net income (loss)		(1)	3	2
Separate account business [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	3	37	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		(2)	(20)	(6)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	3	35	3	35
Unrealized gains (losses) on Level 3 assets and liabilities held at Balance Sheet date recognized in net income (loss)