Reinsurance and Other Monoline Exposures (Details 2) (USD $)											1 Months Ended				1 Months Ended				1 Months Ended
	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2012 Public finance	Dec. 31, 2011 Public finance	Dec. 31, 2012 Other structured finance	Dec. 31, 2011 Other structured finance	Dec. 31, 2012 AGM and AGC	Jan. 12, 2012 AGM and AGC	Dec. 31, 2012 National Public Finance Guarantee Corporation	Jan. 31, 2012 American Overseas Reinsurance Company Limited [Member]	Dec. 31, 2012 American Overseas Reinsurance Company Limited [Member]		Jan. 24, 2012 American Overseas Reinsurance Company Limited [Member]	Jan. 31, 2012 American Overseas Reinsurance Company Limited [Member] Public finance	Jan. 31, 2012 American Overseas Reinsurance Company Limited [Member] Other structured finance	Dec. 31, 2012 Tokio Marine and Nichido Fire Insurance Co Ltd [Member]		Feb. 29, 2012 Tokio Marine and Nichido Fire Insurance Co Ltd [Member] Public finance	Dec. 31, 2012 Radian Asset Assurance Inc [Member]		Dec. 31, 2012 Syncora Guarantee Inc [Member]		Dec. 31, 2012 Mitsui Sumitomo Insurance Co Ltd [Member]		Dec. 31, 2012 Aca Financial Guaranty Corp [Member]		Dec. 31, 2012 Swiss Reinsurance Co [Member]		Dec. 31, 2012 Ambac		Dec. 31, 2012 CIFG Assurance North America Inc. [Member]		Dec. 31, 2012 MBIA Inc.		Dec. 31, 2012 Financial Guaranty Insurance Co [Member]		Dec. 31, 2012 Other		Dec. 31, 2012 Internal Credit Rating Super Senior [Member]	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Other structured finance	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] American Overseas Reinsurance Company Limited [Member]	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] American Overseas Reinsurance Company Limited [Member] Other structured finance	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Tokio Marine and Nichido Fire Insurance Co Ltd [Member]	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Radian Asset Assurance Inc [Member]	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Syncora Guarantee Inc [Member]	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Syncora Guarantee Inc [Member] Other structured finance	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Mitsui Sumitomo Insurance Co Ltd [Member]	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Aca Financial Guaranty Corp [Member]	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Aca Financial Guaranty Corp [Member] Other structured finance	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Swiss Reinsurance Co [Member]	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Ambac	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Ambac Other structured finance	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] CIFG Assurance North America Inc. [Member]	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] CIFG Assurance North America Inc. [Member] Other structured finance	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] MBIA Inc. Other structured finance	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Financial Guaranty Insurance Co [Member] Other structured finance	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Other	Dec. 31, 2012 Internal Credit Rating Super Senior [Member] Other Other structured finance	Dec. 31, 2012 AAA	Dec. 31, 2012 AAA Public finance	Dec. 31, 2012 AAA Other structured finance	Dec. 31, 2012 AAA American Overseas Reinsurance Company Limited [Member]	Dec. 31, 2012 AAA American Overseas Reinsurance Company Limited [Member] Public finance	Dec. 31, 2012 AAA American Overseas Reinsurance Company Limited [Member] Other structured finance	Dec. 31, 2012 AAA Tokio Marine and Nichido Fire Insurance Co Ltd [Member]	Dec. 31, 2012 AAA Radian Asset Assurance Inc [Member]	Dec. 31, 2012 AAA Syncora Guarantee Inc [Member]	Dec. 31, 2012 AAA Syncora Guarantee Inc [Member] Public finance	Dec. 31, 2012 AAA Syncora Guarantee Inc [Member] Other structured finance	Dec. 31, 2012 AAA Mitsui Sumitomo Insurance Co Ltd [Member]	Dec. 31, 2012 AAA Aca Financial Guaranty Corp [Member]	Dec. 31, 2012 AAA Aca Financial Guaranty Corp [Member] Public finance	Dec. 31, 2012 AAA Aca Financial Guaranty Corp [Member] Other structured finance	Dec. 31, 2012 AAA Swiss Reinsurance Co [Member]	Dec. 31, 2012 AAA Ambac	Dec. 31, 2012 AAA Ambac Public finance	Dec. 31, 2012 AAA Ambac Other structured finance	Dec. 31, 2012 AAA CIFG Assurance North America Inc. [Member]	Dec. 31, 2012 AAA CIFG Assurance North America Inc. [Member] Public finance	Dec. 31, 2012 AAA CIFG Assurance North America Inc. [Member] Other structured finance	Dec. 31, 2012 AAA MBIA Inc. Public finance	Dec. 31, 2012 AAA MBIA Inc. Other structured finance	Dec. 31, 2012 AAA Financial Guaranty Insurance Co [Member] Public finance	Dec. 31, 2012 AAA Financial Guaranty Insurance Co [Member] Other structured finance	Dec. 31, 2012 AAA Other	Dec. 31, 2012 AAA Other Public finance	Dec. 31, 2012 AAA Other Other structured finance	Dec. 31, 2012 AA	Dec. 31, 2012 AA Public finance	Dec. 31, 2012 AA Other structured finance	Dec. 31, 2012 AA American Overseas Reinsurance Company Limited [Member]	Dec. 31, 2012 AA American Overseas Reinsurance Company Limited [Member] Public finance	Dec. 31, 2012 AA American Overseas Reinsurance Company Limited [Member] Other structured finance	Dec. 31, 2012 AA Tokio Marine and Nichido Fire Insurance Co Ltd [Member]	Dec. 31, 2012 AA Radian Asset Assurance Inc [Member]	Dec. 31, 2012 AA Syncora Guarantee Inc [Member]	Dec. 31, 2012 AA Syncora Guarantee Inc [Member] Public finance	Dec. 31, 2012 AA Syncora Guarantee Inc [Member] Other structured finance	Dec. 31, 2012 AA Mitsui Sumitomo Insurance Co Ltd [Member]	Dec. 31, 2012 AA Aca Financial Guaranty Corp [Member]	Dec. 31, 2012 AA Aca Financial Guaranty Corp [Member] Public finance	Dec. 31, 2012 AA Aca Financial Guaranty Corp [Member] Other structured finance	Dec. 31, 2012 AA Swiss Reinsurance Co [Member]	Dec. 31, 2012 AA Ambac	Dec. 31, 2012 AA Ambac Public finance	Dec. 31, 2012 AA Ambac Other structured finance	Dec. 31, 2012 AA CIFG Assurance North America Inc. [Member]	Dec. 31, 2012 AA CIFG Assurance North America Inc. [Member] Public finance	Dec. 31, 2012 AA CIFG Assurance North America Inc. [Member] Other structured finance	Dec. 31, 2012 AA MBIA Inc. Public finance	Dec. 31, 2012 AA MBIA Inc. Other structured finance	Dec. 31, 2012 AA Financial Guaranty Insurance Co [Member] Public finance	Dec. 31, 2012 AA Financial Guaranty Insurance Co [Member] Other structured finance	Dec. 31, 2012 AA Other	Dec. 31, 2012 AA Other Public finance	Dec. 31, 2012 AA Other Other structured finance	Dec. 31, 2012 A	Dec. 31, 2012 A Public finance	Dec. 31, 2012 A Other structured finance	Dec. 31, 2012 A American Overseas Reinsurance Company Limited [Member]	Dec. 31, 2012 A American Overseas Reinsurance Company Limited [Member] Public finance	Dec. 31, 2012 A American Overseas Reinsurance Company Limited [Member] Other structured finance	Dec. 31, 2012 A Tokio Marine and Nichido Fire Insurance Co Ltd [Member]	Dec. 31, 2012 A Radian Asset Assurance Inc [Member]	Dec. 31, 2012 A Syncora Guarantee Inc [Member]	Dec. 31, 2012 A Syncora Guarantee Inc [Member] Public finance	Dec. 31, 2012 A Syncora Guarantee Inc [Member] Other structured finance	Dec. 31, 2012 A Mitsui Sumitomo Insurance Co Ltd [Member]	Dec. 31, 2012 A Aca Financial Guaranty Corp [Member]	Dec. 31, 2012 A Aca Financial Guaranty Corp [Member] Public finance	Dec. 31, 2012 A Aca Financial Guaranty Corp [Member] Other structured finance	Dec. 31, 2012 A Swiss Reinsurance Co [Member]	Dec. 31, 2012 A Ambac	Dec. 31, 2012 A Ambac Public finance	Dec. 31, 2012 A Ambac Other structured finance	Dec. 31, 2012 A CIFG Assurance North America Inc. [Member]	Dec. 31, 2012 A CIFG Assurance North America Inc. [Member] Public finance	Dec. 31, 2012 A CIFG Assurance North America Inc. [Member] Other structured finance	Dec. 31, 2012 A MBIA Inc. Public finance	Dec. 31, 2012 A MBIA Inc. Other structured finance	Dec. 31, 2012 A Financial Guaranty Insurance Co [Member] Public finance	Dec. 31, 2012 A Financial Guaranty Insurance Co [Member] Other structured finance	Dec. 31, 2012 A Other	Dec. 31, 2012 A Other Public finance	Dec. 31, 2012 A Other Other structured finance	Dec. 31, 2012 BBB	Dec. 31, 2012 BBB Public finance	Dec. 31, 2012 BBB Other structured finance	Dec. 31, 2012 BBB American Overseas Reinsurance Company Limited [Member]	Dec. 31, 2012 BBB American Overseas Reinsurance Company Limited [Member] Public finance	Dec. 31, 2012 BBB American Overseas Reinsurance Company Limited [Member] Other structured finance	Dec. 31, 2012 BBB Tokio Marine and Nichido Fire Insurance Co Ltd [Member]	Dec. 31, 2012 BBB Radian Asset Assurance Inc [Member]	Dec. 31, 2012 BBB Syncora Guarantee Inc [Member]	Dec. 31, 2012 BBB Syncora Guarantee Inc [Member] Public finance	Dec. 31, 2012 BBB Syncora Guarantee Inc [Member] Other structured finance	Dec. 31, 2012 BBB Mitsui Sumitomo Insurance Co Ltd [Member]	Dec. 31, 2012 BBB Aca Financial Guaranty Corp [Member]	Dec. 31, 2012 BBB Aca Financial Guaranty Corp [Member] Public finance	Dec. 31, 2012 BBB Aca Financial Guaranty Corp [Member] Other structured finance	Dec. 31, 2012 BBB Swiss Reinsurance Co [Member]	Dec. 31, 2012 BBB Ambac	Dec. 31, 2012 BBB Ambac Public finance	Dec. 31, 2012 BBB Ambac Other structured finance	Dec. 31, 2012 BBB CIFG Assurance North America Inc. [Member]	Dec. 31, 2012 BBB CIFG Assurance North America Inc. [Member] Public finance	Dec. 31, 2012 BBB CIFG Assurance North America Inc. [Member] Other structured finance	Dec. 31, 2012 BBB MBIA Inc. Public finance	Dec. 31, 2012 BBB MBIA Inc. Other structured finance	Dec. 31, 2012 BBB Financial Guaranty Insurance Co [Member] Public finance	Dec. 31, 2012 BBB Financial Guaranty Insurance Co [Member] Other structured finance	Dec. 31, 2012 BBB Other	Dec. 31, 2012 BBB Other Public finance	Dec. 31, 2012 BBB Other Other structured finance	Dec. 31, 2012 Below investment grade (BIG)	Dec. 31, 2012 Below investment grade (BIG) Public finance	Dec. 31, 2012 Below investment grade (BIG) Other structured finance	Dec. 31, 2012 Below investment grade (BIG) American Overseas Reinsurance Company Limited [Member]	Dec. 31, 2012 Below investment grade (BIG) American Overseas Reinsurance Company Limited [Member] Public finance	Dec. 31, 2012 Below investment grade (BIG) American Overseas Reinsurance Company Limited [Member] Other structured finance	Dec. 31, 2012 Below investment grade (BIG) Tokio Marine and Nichido Fire Insurance Co Ltd [Member]	Dec. 31, 2012 Below investment grade (BIG) Radian Asset Assurance Inc [Member]	Dec. 31, 2012 Below investment grade (BIG) Syncora Guarantee Inc [Member]	Dec. 31, 2012 Below investment grade (BIG) Syncora Guarantee Inc [Member] Public finance	Dec. 31, 2012 Below investment grade (BIG) Syncora Guarantee Inc [Member] Other structured finance	Dec. 31, 2012 Below investment grade (BIG) Mitsui Sumitomo Insurance Co Ltd [Member]	Dec. 31, 2012 Below investment grade (BIG) Aca Financial Guaranty Corp [Member]	Dec. 31, 2012 Below investment grade (BIG) Aca Financial Guaranty Corp [Member] Public finance	Dec. 31, 2012 Below investment grade (BIG) Aca Financial Guaranty Corp [Member] Other structured finance	Dec. 31, 2012 Below investment grade (BIG) Swiss Reinsurance Co [Member]	Dec. 31, 2012 Below investment grade (BIG) Ambac	Dec. 31, 2012 Below investment grade (BIG) Ambac Public finance	Dec. 31, 2012 Below investment grade (BIG) Ambac Other structured finance	Dec. 31, 2012 Below investment grade (BIG) CIFG Assurance North America Inc. [Member]	Dec. 31, 2012 Below investment grade (BIG) CIFG Assurance North America Inc. [Member] Public finance	Dec. 31, 2012 Below investment grade (BIG) CIFG Assurance North America Inc. [Member] Other structured finance	Dec. 31, 2012 Below investment grade (BIG) MBIA Inc. Public finance	Dec. 31, 2012 Below investment grade (BIG) MBIA Inc. Other structured finance	Dec. 31, 2012 Below investment grade (BIG) Financial Guaranty Insurance Co [Member] Public finance	Dec. 31, 2012 Below investment grade (BIG) Financial Guaranty Insurance Co [Member] Other structured finance	Dec. 31, 2012 Below investment grade (BIG) Other	Dec. 31, 2012 Below investment grade (BIG) Other Public finance	Dec. 31, 2012 Below investment grade (BIG) Other Other structured finance
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Fixed maturity securities wrapped by monoline reinsurer										$ 667,000,000																				$ 517,000,000								$ 31,000,000
Ceded Par Amount	32,146,000,000	[1]	56,294,000,000	25,715,000,000	48,146,000,000	6,431,000,000	8,148,000,000					5,250,000,000	[1]				8,369,000,000	[1],[2]		9,808,000,000	[1],[3]	4,156,000,000	[1]	2,232,000,000	[1],[2]	819,000,000	[1]	429,000,000	[1]	85,000,000	[1]	65,000,000	[1]	0	[1],[4]	0	[1]	933,000,000	[1]	559,000,000		10,000,000		313,000,000	229,000,000	0		7,000,000	0		0	0		0				0		2,744,000,000			256,000,000			1,072,000,000	1,257,000,000	0			151,000,000	0			8,000,000	0			0							0			6,504,000,000			334,000,000			1,396,000,000	3,237,000,000	241,000,000			702,000,000	474,000,000			6,000,000	0			0							114,000,000			10,869,000,000			2,395,000,000			2,457,000,000	2,978,000,000	761,000,000			865,000,000	325,000,000			261,000,000	85,000,000			0							742,000,000			9,038,000,000			1,877,000,000			2,411,000,000	1,598,000,000	2,495,000,000			449,000,000	20,000,000			111,000,000	0			0							77,000,000			2,432,000,000			378,000,000			720,000,000	509,000,000	659,000,000			58,000,000	0			43,000,000	0			65,000,000							0
Ceded Par Outstanding	25,531,000,000											44,000,000					0	[2]		0	[3]	1,993,000,000		0	[2]	6,000,000		0		7,122,000,000		255,000,000		10,814,000,000	[4]	3,227,000,000		2,070,000,000			372,000,000		0				0			0			0		0	0	372,000,000		0		69,000,000	853,000,000		0	0				0	203,000,000			0	0			0	15,000,000		0	0	69,000,000	0	0	635,000,000		0	0		4,207,000,000	1,432,000,000		0	0				25,000,000	0			3,000,000	0			1,471,000,000	54,000,000		11,000,000	0	2,567,000,000	1,378,000,000	130,000,000	0		0	0		11,293,000,000	509,000,000		13,000,000	0				377,000,000	78,000,000			0	0			3,431,000,000	235,000,000		69,000,000	0	4,367,000,000	47,000,000	966,000,000	149,000,000		2,070,000,000	0		4,625,000,000	283,000,000		19,000,000	0				772,000,000	0			3,000,000	0			1,194,000,000	78,000,000		130,000,000	0	1,947,000,000	205,000,000	560,000,000	0		0	0		1,085,000,000	803,000,000		12,000,000	0				334,000,000	204,000,000			0	0			333,000,000	311,000,000		45,000,000	0	0	234,000,000	361,000,000	54,000,000		0	0
Assumed Par Outstanding	38,757,000,000											1,382,000,000					937,000,000	[2]		24,000,000	[3]	162,000,000		0	[2]	1,000,000		0		20,579,000,000		5,523,000,000		8,143,000,000	[4]	1,961,000,000		45,000,000
Ceded par outstanding related to insured credit derivatives	3,928,000,000
Assumed Premium Receivable, net of Commissions	86,000,000											0					0			0		0		0				0		76,000,000		0		1,000,000		9,000,000		0
Ceded Premium Payable, net of Commissions	(173,000,000)											(20,000,000)					(27,000,000)			(12,000,000)		(43,000,000)		(5,000,000)				(3,000,000)		0		0		0		0		(63,000,000)
Assumed Expected Loss and LAE	(122,000,000)											0					0			0		28,000,000		0				0		(73,000,000)		0		(19,000,000)		(58,000,000)		0
Ceded Expected Loss and LAE	53,000,000											(4,000,000)					37,000,000			5,000,000		1,000,000		9,000,000				2,000,000		0		3,000,000		0		0		0
Minimum net losses required for attachment of excess of loss reinsurance facility								2,000,000,000
Amount of losses covered under the facility								600,000,000
Amount of losses which the reinsurers will assume on pro rata basis									435,000,000
Remaining amount of losses covered under the facility								165,000,000
Amount agreed to be reassumed											12,900,000,000								6,200,000,000
Approximate amount of insurance risk agreed to be assumed											1,800,000,000
Payment receivable for re-assumption of ceded risk														86,000,000
Percentage of obligations insured															96.00%	4.00%
Payment receivable in connection with reinsurance														22,000,000
Premiums paid during the period	22,000,000
Remaining insurance premium payable	22,000,000
Collateral Posted by Non-affiliated Reinsurers	$ 999,000,000

[1] Includes $3,928 million in ceded par outstanding related to insured credit derivatives.

[2] The Company has structural collateral agreements satisfying the triple-A credit requirement of S&P and/or Moody’s.

[3] Represents “Withdrawn Rating.”

[4] MBIA Inc. includes various subsidiaries which are rated B, BBB by S&P and Caa2, B3, Baa2, WR and NR by Moody’s.