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, 2013	Mar. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 1,393	$ 1,751
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(4)	11
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	9	7
Purchases	465	411
Sales	(165)	(183)
Settlements	(65)	(95)
Transfers into Level 3	26	33
Transfers out of Level 3	(59)	(84)
Balance, Ending, Assets	1,600	1,851
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(16)	(3)
Corporate and other bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	219	482
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)	2	4
Purchases	110	79
Sales	(17)	(86)
Settlements	(20)	(19)
Transfers into Level 3	26	33
Transfers out of Level 3	(18)	(10)
Balance, Ending, Assets	302	486
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(1)
States, municipalities and political subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	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)		2
Purchases	85
Sales	(47)
Settlements	(2)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	129	173
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	413	452
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	3	1
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)		(4)
Purchases	61	38
Sales
Settlements	(11)	(7)
Transfers into Level 3
Transfers out of Level 3	(16)	(33)
Balance, Ending, Assets	450	447
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date 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	129	59
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)	5	4
Purchases	73	42
Sales
Settlements	(7)
Transfers into Level 3
Transfers out of Level 3	(24)
Balance, Ending, Assets	177	105
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	368	343
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)	1	4
Purchases	136	176
Sales	(99)	(77)
Settlements	(13)	(25)
Transfers into Level 3
Transfers out of Level 3		(41)
Balance, Ending, Assets	396	384
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)
Total asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	910	854
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	7	5
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	6	4
Purchases	270	256
Sales	(99)	(77)
Settlements	(31)	(32)
Transfers into Level 3
Transfers out of Level 3	(40)	(74)
Balance, Ending, Assets	1,023	936
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date 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	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)
Purchases		53
Sales
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	26	53
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	1,251	1,507
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	4	8
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	8	10
Purchases	465	388
Sales	(163)	(163)
Settlements	(53)	(51)
Transfers into Level 3	26	33
Transfers out of Level 3	(58)	(84)
Balance, Ending, Assets	1,480	1,648
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(1)
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	34	67
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(15)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	1	(3)
Purchases		11
Sales		(1)
Settlements
Transfers into Level 3
Transfers out of Level 3	(1)
Balance, Ending, Assets	19	74
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	(15)	(2)
Other invested assets, including derivatives, net
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets		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
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	(1)	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	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		12
Sales	(1)
Settlements		(39)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	5
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	100	117
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	7	3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)
Purchases
Sales
Settlements	(12)	(5)
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	95	115
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)		(1)
Separate account business [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	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		(19)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance, Ending, Assets	2	4
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)