Loss And Loss Adjustment Expense Reserves (Schedule Of Economic Loss Activity) (Details) (USD $) In Millions			6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011 Aggregate Losses and LAE [Member]	Jun. 30, 2011 Aggregate Losses and LAE [Member] Financial Guarantee Insurance Losses And LAE [Member]		Jun. 30, 2011 Aggregate Losses and LAE [Member] Financial Guarantee Insurance Losses And LAE [Member] RMBS [Member]		Jun. 30, 2011 Aggregate Losses and LAE [Member] Financial Guarantee Insurance Losses And LAE [Member] Non-RMBS [Member]		Jun. 30, 2011 Aggregate Losses and LAE [Member] Financial Guarantee Insurance Losses And LAE Related To Consolidated VIEs (Eliminated In Consolidation) [Member]		Jun. 30, 2011 Aggregate Losses and LAE [Member] Financial Guarantee Insurance Losses And LAE Related To Consolidated VIEs (Eliminated In Consolidation) [Member] RMBS [Member]		Jun. 30, 2011 Aggregate Losses and LAE [Member] Financial Guarantee Insurance Losses And LAE Related To Consolidated VIEs (Eliminated In Consolidation) [Member] Non-RMBS [Member]		Jun. 30, 2011 Aggregate Losses and LAE [Member] Insured Credit Derivative Impairments And LAE [Member]		Jun. 30, 2011 Aggregate Losses and LAE [Member] Insured Credit Derivative Impairments And LAE [Member] Non-RMBS [Member]		Jun. 30, 2011 Aggregate Losses and LAE [Member] RMBS [Member]	Jun. 30, 2011 Aggregate Losses and LAE [Member] Non-RMBS [Member]	Jun. 30, 2011 Aggregate Loss and LAE Reserves [Member]	Dec. 31, 2010 Aggregate Loss and LAE Reserves [Member]	Jun. 30, 2011 Aggregate Loss and LAE Reserves [Member] Financial Guarantee Insurance [Member]		Dec. 31, 2010 Aggregate Loss and LAE Reserves [Member] Financial Guarantee Insurance [Member]		Jun. 30, 2011 Aggregate Loss and LAE Reserves [Member] Financial Guarantee Insurance Related To Consolidated VIEs (Eliminated In Consolidation) [Member]		Dec. 31, 2010 Aggregate Loss and LAE Reserves [Member] Financial Guarantee Insurance Related To Consolidated VIEs (Eliminated In Consolidation) [Member]		Jun. 30, 2011 Aggregate Loss and LAE Reserves [Member] Insured Credit Derivative Impairments And LIE (Statutory Basis) [Member]		Dec. 31, 2010 Aggregate Loss and LAE Reserves [Member] Insured Credit Derivative Impairments And LIE (Statutory Basis) [Member]		Jun. 30, 2011 Aggregate Loss and LAE Reserves [Member] Reinsurance [Member]	Dec. 31, 2010 Aggregate Loss and LAE Reserves [Member] Reinsurance [Member]	Jun. 30, 2011 Financial Guarantee Insurance [Member]		Jun. 30, 2010 Financial Guarantee Insurance [Member]		Jun. 30, 2011 Financial Guarantee Insurance Related To Consolidated VIEs (Eliminated In Consolidation) [Member]		Jun. 30, 2010 Financial Guarantee Insurance Related To Consolidated VIEs (Eliminated In Consolidation) [Member]		Jun. 30, 2011 Insured Credit Derivative Impairments And LIE (Statutory Basis) [Member]		Jun. 30, 2010 Insured Credit Derivative Impairments And LIE (Statutory Basis) [Member]		Jun. 30, 2011 Reinsurance [Member]	Jun. 30, 2010 Reinsurance [Member]
Total economic losses and LAE			$ (8)	$ 14	[1]	$ (50)	[1]	$ 64	[1]	$ 12	[2]	$ (39)	[2]	$ 51	[2]	$ (34)	[3]	$ (34)	[3]	$ (89)	$ 81
Total aggregate loss and LAE reserves																						3,248	3,981	865	[4]	1,129	[4]	352	[5]	377	[5]	2,047	[6]	2,490	[6]	(16)	(15)
Total aggregate insurance loss recoverable	$ 3,875	$ 3,662																																				$ 2,658	[7]	$ 2,531	[7]	$ 1,159	[8]	$ 1,061	[8]	$ 66	[9]	$ 74	[9]	$ (8)	$ (4)

[1]

[2] Represents losses and LAE eliminated upon the consolidation of insured VIEs.

[3] Represents statutory losses and LAE for insurance contracts accounted for as derivatives. Realized and unrealized gains and losses on these contracts under U.S. GAAP are recorded in "Net change in fair value of insured derivatives" on the Company's consolidated statement of operations.

[4] Represents "Loss and loss adjustment expense reserves" as reported on the Company's consolidated balance sheets.

[5] Represents loss and LAE reserves eliminated upon the consolidation of insured VIEs.

[6] Represents statutory loss and LAE reserves for insurance contracts accounted for as derivatives under U.S. GAAP. The fair values of these contracts are recorded in "Derivative liabilities" on the Company's consolidated balance sheets.

[7] Represents "Insurance loss recoverable" as reported on the Company's consolidated balance sheets.

[8] Represents insurance loss recoverable eliminated upon the consolidation of insured VIEs.

[9] Represents statutory recoveries for insurance contracts accounted for as derivatives under U.S. GAAP. The fair values of these contracts are recorded in "Derivative liabilities" on the Company's consolidated balance sheets.