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
	Mar. 31, 2012	Mar. 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)	11	19
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	7	10
Purchases	411	316
Sales	(183)	(170)
Settlements	(95)	(166)
Transfers into Level 3	33	9
Transfers out of Level 3	(84)	(91)
Balance, Ending, Assets	1,851	2,267
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 recognized in net income (loss)	(3)	(3)
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)	8	15
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	10	11
Purchases	388	289
Sales	(163)	(140)
Settlements	(51)	(159)
Transfers into Level 3	33	9
Transfers out of Level 3	(84)	(81)
Balance, Ending, Assets	1,648	2,036
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 recognized in net income (loss)
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)	3	4
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	4	(5)
Purchases	79	42
Sales	(86)	(20)
Settlements	(19)	(27)
Transfers into Level 3	33	9
Transfers out of Level 3	(10)	(50)
Balance, Ending, Assets	486	577
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 recognized in net income (loss)
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)	2	1
Purchases
Sales
Settlements		(79)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	173	188
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 recognized in net income (loss)
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	8
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	4	18
Purchases	256	247
Sales	(77)	(117)
Settlements	(32)	(53)
Transfers into Level 3
Transfers out of Level 3	(74)	(31)
Balance, Ending, Assets	936	1,271
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 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)	1	1
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(4)	2
Purchases	38	47
Sales		(26)
Settlements	(7)	(22)
Transfers into Level 3
Transfers out of Level 3	(33)	(31)
Balance, Ending, Assets	447	738
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 recognized in net income (loss)
Commercial mortgage-backed [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)		3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	4	16
Purchases	42
Sales		(4)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	105	88
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 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)	4	4
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	4
Purchases	176	200
Sales	(77)	(87)
Settlements	(25)	(31)
Transfers into Level 3
Transfers out of Level 3	(41)
Balance, Ending, Assets	384	445
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 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		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		(3)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	53
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 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)		(1)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(3)	(1)
Purchases	11	15
Sales	(1)	(9)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	74	30
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 recognized in net income (loss)	(2)	(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	25
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)		2
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	8
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 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	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	12	12
Sales
Settlements	(39)	(2)
Transfers into Level 3
Transfers out of Level 3		(10)
Balance, Ending, Assets		27
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 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)	3	3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)
Purchases
Sales
Settlements	(5)	(5)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	115	127
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 recognized in net income (loss)	(1)	(1)
Seperate 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	(19)	(2)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	4	39
Unrealized gains (losses) on Level 3 assets and liabilities held at March 31 recognized in net income (loss)