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, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 1,600	$ 1,851	$ 1,393	$ 1,751
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(1)	28	(5)	39
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(1)	7	8	14
Purchases	143	378	608	789
Sales	(153)	(180)	(318)	(363)
Settlements	(50)	(164)	(115)	(259)
Transfers into Level 3	30	9	56	42
Transfers out of Level 3	(115)	(56)	(174)	(140)
Balance, Ending, Assets	1,453	1,873	1,453	1,873
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(10)	2	(26)
Corporate and other bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	302	486	219	482
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	3	1	6
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(3)	2	(1)	6
Purchases	13	68	123	147
Sales	(73)	(27)	(90)	(113)
Settlements	(6)	(13)	(26)	(32)
Transfers into Level 3		9	26	42
Transfers out of Level 3	(32)	(40)	(50)	(50)
Balance, Ending, Assets	202	488	202	488
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(1)		(2)
States, municipalities and political subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	129	173	96	171
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)	4	1	4	3
Purchases	37		122
Sales	(32)		(79)
Settlements	(3)	(85)	(5)	(85)
Transfers into Level 3	5		5
Transfers out of Level 3
Balance, Ending, Assets	140	89	140	89
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	450	447	413	452
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(1)	1	2	2
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(1)	(18)	(1)	(22)
Purchases	50	22	111	60
Sales	(10)		(10)
Settlements	(21)	(9)	(32)	(16)
Transfers into Level 3	4		4
Transfers out of Level 3	(43)		(59)	(33)
Balance, Ending, Assets	428	443	428	443
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(2)		(2)
Commercial mortgage-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	177	105	129	59
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)		2	1	2
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	4	4	9	8
Purchases	5	87	78	129
Sales		(12)		(12)
Settlements	(2)	(4)	(9)	(4)
Transfers into Level 3	21		21
Transfers out of Level 3	(40)	(16)	(64)	(16)
Balance, Ending, Assets	165	166	165	166
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	396	384	368	343
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)		2	3	6
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(3)	(1)	(2)	3
Purchases	38	182	174	358
Sales	(33)	(99)	(132)	(176)
Settlements	(11)	(34)	(24)	(59)
Transfers into Level 3
Transfers out of Level 3				(41)
Balance, Ending, Assets	387	434	387	434
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(1)		(1)
Total asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	1,023	936	910	854
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(1)	5	6	10
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)		(15)	6	(11)
Purchases	93	291	363	547
Sales	(43)	(111)	(142)	(188)
Settlements	(34)	(47)	(65)	(79)
Transfers into Level 3	25		25
Transfers out of Level 3	(83)	(16)	(123)	(90)
Balance, Ending, Assets	980	1,043	980	1,043
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(3)		(3)
Redeemable preferred stock [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	26	53	26
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)
Purchases				53
Sales		(26)		(26)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	25	27	25	27
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)
Fixed maturity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	1,480	1,648	1,251	1,507
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)		8	4	16
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)		(12)	8	(2)
Purchases	143	359	608	747
Sales	(148)	(164)	(311)	(327)
Settlements	(43)	(145)	(96)	(196)
Transfers into Level 3	30	9	56	42
Transfers out of Level 3	(115)	(56)	(173)	(140)
Balance, Ending, Assets	1,347	1,647	1,347	1,647
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(4)		(5)
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	19	74	34	67
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(5)		(20)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(1)	19		16
Purchases		15		26
Sales		(15)		(16)
Settlements
Transfers into Level 3
Transfers out of Level 3			(1)
Balance, Ending, Assets	13	93	13	93
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(5)	(1)	(20)	(3)
Other invested assets, including derivatives, net
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	(1)	10		10
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)
Settlements	1		1
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets		10		10
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)
Short term investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	5		6	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
Sales	(5)		(6)
Settlements				(39)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets		4		4
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	95	115	100	117
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	4	20	11	23
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)
Purchases
Sales
Settlements	(8)	(19)	(20)	(24)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	91	116	91	116
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(1)	3	(1)	3
Separate account business [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	2	4	2	23
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)		(20)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	2	3	2	3
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)