Fair Value Of Financial Instruments (Company's Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	$ 18,000	$ 21,227
Fair value financial liabilities measured on recurring basis	12,417	13,575
Variable Interest Entity, Primary Beneficiary [Member] | Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	2,218	2,183
Variable Interest Entity, Primary Beneficiary [Member] | Loans Receivable [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	2,218	2,183
Variable Interest Entity, Primary Beneficiary [Member] | Loan Repurchase Commitments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		835
Variable Interest Entity, Primary Beneficiary [Member] | Loan Repurchase Commitments [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		835
Loan Repurchase Commitments [Member] | Assets Of Consolidated VIEs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	938
Loan Repurchase Commitments [Member] | Assets Of Consolidated VIEs [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	938
Variable Interest Entity, Primary Beneficiary [Member] | Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	643	828
Variable Interest Entity, Primary Beneficiary [Member] | Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	437	583
Variable Interest Entity, Primary Beneficiary [Member] | Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	206	245
Variable Interest Entity, Primary Beneficiary [Member] | Residential Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	4	37
Variable Interest Entity, Primary Beneficiary [Member] | Residential Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	4	37
Variable Interest Entity, Primary Beneficiary [Member] | Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	612	930
Variable Interest Entity, Primary Beneficiary [Member] | Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	595	907
Variable Interest Entity, Primary Beneficiary [Member] | Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	17	23
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	3,590	5,431
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Non-Agency [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1,718	2,746
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Non-Agency [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1,703	2,706
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Non-Agency [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	15	40
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | Other Asset-Backed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	346	435
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | Other Asset-Backed [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	275	352
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | Other Asset-Backed [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	71	83
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | State And Municipal Bonds [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		4
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | State And Municipal Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		4
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | U.S. Treasury And Government Agency [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		4
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | U.S. Treasury And Government Agency [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		4
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Corporate Obligations [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	267	447
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Corporate Obligations [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		7
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Corporate Obligations [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	204	360
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Corporate Obligations [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	63	80
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		11
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	3,218	4,949
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	372	471
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Assets [Member] | Credit Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	708	687
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Assets [Member] | Credit Derivatives [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	708	687
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Assets [Member] | Interest Rate Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	5	12
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Assets [Member] | Interest Rate Derivatives [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	5	12
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Liabilities [Member] | Credit Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	1,473	1,455
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Liabilities [Member] | Credit Derivatives [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	1,473	1,455
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Liabilities [Member] | Interest Rate Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	397	635
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	397	635
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Liabilities [Member] | Currency Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	18	14
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Liabilities [Member] | Currency Derivatives [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	18	14
Variable Interest Entity, Primary Beneficiary [Member] | Money Market Securities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	218	150
Variable Interest Entity, Primary Beneficiary [Member] | Money Market Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	218	150
Variable Interest Entity, Primary Beneficiary [Member] | Variable Interest Entity Notes [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	5,123	6,680
Variable Interest Entity, Primary Beneficiary [Member] | Variable Interest Entity Notes [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	1,992	2,007
Variable Interest Entity, Primary Beneficiary [Member] | Variable Interest Entity Notes [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	3,131	4,673
Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Asset-Backed Securities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	151	299
Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Asset-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	84	108
Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Asset-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	67	191
Residential Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1,420	1,589
Residential Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1,419	1,548
Residential Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1	41
Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	67	161
Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	35	120
Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	32	41
Fixed-Maturity Investments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	9,454	11,159
Fixed-Maturity Investments [Member] | Taxable Bonds [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	6,594	8,304
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Non-Agency [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	446	462
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Non-Agency [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	421	414
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Non-Agency [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	25	48
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Asset-Backed Securities [Member] | Other Asset-Backed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	457	660
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Asset-Backed Securities [Member] | Other Asset-Backed [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	185	310
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Asset-Backed Securities [Member] | Other Asset-Backed [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	272	350
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | U.S. Treasury And Government Agency [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	898	1,064
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | U.S. Treasury And Government Agency [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	749	915
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | U.S. Treasury And Government Agency [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	149	149
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Foreign Governments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	376	469
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Foreign Governments [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	295	409
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Foreign Governments [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	70	49
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Foreign Governments [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	11	11
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Corporate Obligations [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1,927	2,848
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Corporate Obligations [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Corporate Obligations [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1,584	2,602
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Corporate Obligations [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	342	246
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | State And Municipal Bonds [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	852	752
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | State And Municipal Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	852	738
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | State And Municipal Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		14
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1,045	1,324
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	4,799	6,038
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	750	942
Fixed-Maturity Investments [Member] | State And Municipal Taxable Bonds [Member] | Tax-Exempt Bonds [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	2,845	2,823
Fixed-Maturity Investments [Member] | State And Municipal Taxable Bonds [Member] | Tax-Exempt Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	2,815	2,787
Fixed-Maturity Investments [Member] | State And Municipal Taxable Bonds [Member] | Tax-Exempt Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	30	36
Fixed-Maturity Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1,045	1,337
Fixed-Maturity Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	7,629	8,844
Fixed-Maturity Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	780	978
Fixed-Maturity Investments [Member] | Other-Fixed Maturity Investments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	15	32
Fixed-Maturity Investments [Member] | Other-Fixed Maturity Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		13
Fixed-Maturity Investments [Member] | Other-Fixed Maturity Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	15	19
Other Long Term Investments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		21
Other Long Term Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		16
Other Long Term Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		5
Other Long Term Investments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	27
Other Long Term Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	27
Derivative Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	2	4
Derivative Assets [Member] | Credit Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		3
Derivative Assets [Member] | Credit Derivatives [Member] | Non-Insured Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1
Derivative Assets [Member] | Credit Derivatives [Member] | Non-Insured Derivatives [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1
Derivative Assets [Member] | Credit Derivatives [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		3
Derivative Assets [Member] | Interest Rate Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		62
Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	92
Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	89
Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	3
Derivative Assets [Member] | Interest Rate Derivatives [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		57
Derivative Assets [Member] | Interest Rate Derivatives [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		5
Derivative Assets [Member] | Other Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		(61)
Derivative Assets [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	(91)
Derivative Assets [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member] | Counterparty And Cash Collateral Netting [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	(91)
Derivative Assets [Member] | Other Derivatives [Member] | Counterparty And Cash Collateral Netting [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis		(61)
Derivative Assets [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	90	60
Derivative Assets [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	3	5
Derivative Assets [Member] | Counterparty And Cash Collateral Netting [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	(91)	(61)
Derivative Liabilities [Member] | Credit Derivatives [Member] | Insured Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	4,901	4,375
Derivative Liabilities [Member] | Credit Derivatives [Member] | Insured Derivatives [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	21	25
Derivative Liabilities [Member] | Credit Derivatives [Member] | Insured Derivatives [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	4,880	4,350
Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	450	297
Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	450	297
Derivative Liabilities [Member] | Currency Derivatives [Member] | Non-Insured Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	6	6
Derivative Liabilities [Member] | Currency Derivatives [Member] | Non-Insured Derivatives [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	6	6
Derivative Liabilities [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	(91)	(61)
Derivative Liabilities [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member] | Counterparty And Cash Collateral Netting [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	(91)	(61)
Other Liabilities [Member] | Warrants [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	12	58
Other Liabilities [Member] | Warrants [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	12	58
Total Investments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	10,321	11,925
Total Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1,765	1,906
Total Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	7,775	9,041
Total Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	781	978
Perpetual Preferred Securities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	147	192
Perpetual Preferred Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	146	192
Perpetual Preferred Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1
Money Market Securities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	693	553
Money Market Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	693	553
Medium-Term Notes [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	128	116
Medium-Term Notes [Member] | Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial liabilities measured on recurring basis	128	116
Fair Value, Inputs, Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	1,983	2,067
Fair Value, Inputs, Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	11,088	14,062
Fair value financial liabilities measured on recurring basis	2,878	3,028
Fair Value, Inputs, Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	5,020	5,159
Fair value financial liabilities measured on recurring basis	9,630	10,608
Counterparty And Cash Collateral Netting [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value financial assets measured on recurring basis	(91)	(61)
Fair value financial liabilities measured on recurring basis	$ (91)	$ (61)