Financial Guaranty Insurance Losses (Details 6) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Sep. 30, 2013 risk		Dec. 31, 2012 risk
Outstanding exposure:
Reserves (salvage)	$ 293	[1]	$ 133	[1]
Effect of Consolidating FG VIEs
Outstanding exposure:
Present value of expected cash flows	(52)
Financial guaranty
Outstanding exposure:
Present value of expected cash flows	(552)		(451)
Reserves (salvage)	273		106
Financial guaranty | BIG 1 | Gross
Financial Guaranty Insurance BIG Transaction Loss Summary
Number of risks	154	[2],[3]	163	[2],[3]
Remaining weighted-average contract period (in years)	9 years 8 months 48 days	[3]	10 years 2 months	[3]
Outstanding exposure:
Principal	8,795	[3]	9,462	[3]
Interest	4,432	[3]	4,475	[3]
Total	13,227	[3],[4]	13,937	[3],[4]
Expected cash outflows (inflows)	1,593	[3]	1,914	[3]
Potential recoveries	(1,759)	[3],[5]	(2,356)	[3],[5]
Subtotal	(166)	[3]	(442)	[3]
Discount	23	[3]	12	[3]
Present value of expected cash flows	(143)	[3]	(430)	[3]
Deferred premium revenue	359	[3]	265	[3]
Reserves (salvage)	(180)	[3],[6]	(485)	[3],[6]
Financial guaranty | BIG 1 | Ceded
Financial Guaranty Insurance BIG Transaction Loss Summary
Number of risks	52	[2],[3]	66	[2],[3]
Remaining weighted-average contract period (in years)	7 years 2 months 12 days	[3]	9 years 2 months	[3]
Outstanding exposure:
Principal	1,342	[3]	1,533	[3]
Interest	499	[3]	591	[3]
Total	1,841	[3],[4]	2,124	[3],[4]
Expected cash outflows (inflows)	(508)	[3]	(687)	[3]
Potential recoveries	512	[3],[5]	677	[3],[5]
Subtotal	4	[3]	(10)	[3]
Discount	(1)	[3]	8	[3]
Present value of expected cash flows	3	[3]	(2)	[3]
Deferred premium revenue	(60)	[3]	(32)	[3]
Reserves (salvage)	8	[3],[6]	10	[3],[6]
Financial guaranty | BIG 2 | Gross
Financial Guaranty Insurance BIG Transaction Loss Summary
Number of risks	76	[2],[3]	76	[2],[3]
Remaining weighted-average contract period (in years)	8 years 6 months 0 days	[3]	10 years 6 months 36 days	[3]
Outstanding exposure:
Principal	2,772	[3]	2,248	[3]
Interest	1,350	[3]	1,357	[3]
Total	4,122	[3],[4]	3,605	[3],[4]
Expected cash outflows (inflows)	806	[3]	863	[3]
Potential recoveries	(395)	[3],[5]	(509)	[3],[5]
Subtotal	411	[3]	354	[3]
Discount	(135)	[3]	(107)	[3]
Present value of expected cash flows	276	[3]	247	[3]
Deferred premium revenue	163	[3]	227	[3]
Reserves (salvage)	142	[3],[6]	102	[3],[6]
Financial guaranty | BIG 2 | Ceded
Financial Guaranty Insurance BIG Transaction Loss Summary
Number of risks	24	[2],[3]	22	[2],[3]
Remaining weighted-average contract period (in years)	9 years 6 months 0 days	[3]	15 years 1 month	[3]
Outstanding exposure:
Principal	235	[3]	132	[3]
Interest	142	[3]	127	[3]
Total	377	[3],[4]	259	[3],[4]
Expected cash outflows (inflows)	(93)	[3]	(58)	[3]
Potential recoveries	25	[3],[5]	18	[3],[5]
Subtotal	(68)	[3]	(40)	[3]
Discount	26	[3]	14	[3]
Present value of expected cash flows	(42)	[3]	(26)	[3]
Deferred premium revenue	(23)	[3]	(15)	[3]
Reserves (salvage)	(32)	[3],[6]	(18)	[3],[6]
Financial guaranty | BIG 3 | Gross
Financial Guaranty Insurance BIG Transaction Loss Summary
Number of risks	136	[2],[3]	131	[2],[3]
Remaining weighted-average contract period (in years)	10 years 7 months 42 days	[3]	9 years	[3]
Outstanding exposure:
Principal	3,884	[3]	6,024	[3]
Interest	1,531	[3]	1,881	[3]
Total	5,415	[3],[4]	7,905	[3],[4]
Expected cash outflows (inflows)	2,686	[3]	2,720	[3]
Potential recoveries	(1,766)	[3],[5]	(1,911)	[3],[5]
Subtotal	920	[3]	809	[3]
Discount	(391)	[3]	(216)	[3]
Present value of expected cash flows	529	[3]	593	[3]
Deferred premium revenue	447	[3]	604	[3]
Reserves (salvage)	351	[3],[6]	347	[3],[6]
Financial guaranty | BIG 3 | Ceded
Financial Guaranty Insurance BIG Transaction Loss Summary
Number of risks	40	[2],[3]	41	[2],[3]
Remaining weighted-average contract period (in years)	7 years 9 months 18 days	[3]	6 years	[3]
Outstanding exposure:
Principal	296	[3]	481	[3]
Interest	93	[3]	117	[3]
Total	389	[3],[4]	598	[3],[4]
Expected cash outflows (inflows)	(123)	[3]	(146)	[3]
Potential recoveries	97	[3],[5]	117	[3],[5]
Subtotal	(26)	[3]	(29)	[3]
Discount	7	[3]	2	[3]
Present value of expected cash flows	(19)	[3]	(27)	[3]
Deferred premium revenue	(52)	[3]	(83)	[3]
Reserves (salvage)	(8)	[3],[6]	(3)	[3],[6]
Financial guaranty | Below investment grade (BIG)
Financial Guaranty Insurance BIG Transaction Loss Summary
Number of risks	366	[2],[3]	370	[2],[3]
Remaining weighted-average contract period (in years)	10 years 1 month 6 days	[3]	10 years 0 months	[3]
Outstanding exposure:
Principal	13,578	[3]	15,588	[3]
Interest	6,579	[3]	6,878	[3]
Total	20,157	[3],[4]	22,466	[3],[4]
Expected cash outflows (inflows)	3,658	[3]	3,868	[3]
Potential recoveries	(2,685)	[3],[5]	(3,166)	[3],[5]
Subtotal	973	[3]	702	[3]
Discount	(421)	[3]	(251)	[3]
Present value of expected cash flows	552	[3]	451	[3]
Deferred premium revenue	644	[3]	715	[3]
Reserves (salvage)	273	[3],[6]	106	[3],[6]
Financial guaranty | Below investment grade (BIG) | Total BIG, Net
Financial Guaranty Insurance BIG Transaction Loss Summary
Number of risks	366	[2],[3]	370	[2],[3]
Remaining weighted-average contract period (in years)	10 years 1 month 6 days	[3]	10 years	[3]
Outstanding exposure:
Principal	13,578	[3]	15,588	[3]
Interest	6,579	[3]	6,878	[3]
Total	20,157	[3],[4]	22,466	[3],[4]
Expected cash outflows (inflows)	4,361	[3]	4,606	[3]
Potential recoveries	(3,286)	[3],[5]	(3,964)	[3],[5]
Subtotal	1,075	[3]	642	[3]
Discount	(471)	[3]	(287)	[3]
Present value of expected cash flows	604	[3]	355	[3]
Deferred premium revenue	834	[3]	966	[3]
Reserves (salvage)	281	[3],[6]	(47)	[3],[6]
Financial guaranty | Below investment grade (BIG) | Effect of Consolidating FG VIEs
Financial Guaranty Insurance BIG Transaction Loss Summary
Number of risks	0	[2],[3]	0	[2],[3]
Outstanding exposure:
Principal	0	[3]	0	[3]
Interest	0	[3]	0	[3]
Total	0	[3],[4]	0	[3],[4]
Expected cash outflows (inflows)	(703)	[3]	(738)	[3]
Potential recoveries	601	[3],[5]	798	[3],[5]
Subtotal	(102)	[3]	60	[3]
Discount	50	[3]	36	[3]
Present value of expected cash flows	(52)	[3]	96	[3]
Deferred premium revenue	(190)	[3]	(251)	[3]
Reserves (salvage)	$ (8)	[3],[6]	$ 153	[3]

[1] (1)See “Components of Net Reserves (Salvage)” table for loss and LAE reserve and salvage and subrogation recoverable components.

[2] A risk represents the aggregate of the financial guaranty policies that share the same revenue source for purposes of making Debt Service payments. The ceded number of risks represents the number of risks for which the Company ceded a portion of its exposure.

[3] In Third Quarter 2013, the Company adjusted its approach to assigning internal ratings. See "Refinement of Approach to Internal Credit Ratings and Surveillance Categories" in Note 3, Outstanding Exposure. This approach is reflected in the "Financial Guaranty Insurance BIG Transaction Loss Summary" tables as of both September 30, 2013 and December 31, 2012.

[4] Includes BIG amounts related to FG VIEs.

[5] Includes estimated future recoveries for breaches of R&W as well as excess spread, and draws on HELOCs.

[6] See table “Components of net reserves (salvage).”