Financial Guaranty Insurance Losses (Details 5) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Guarantor Obligations [Line Items]
Subtotal	$ 66	$ 88	$ 95	$ 460
Effect of consolidating FG VIEs	(11)	(2)	(26)	(14)
Loss and LAE	55	86	69	446
Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	66	88	95	466
Other
Guarantor Obligations [Line Items]
Subtotal	0	0	0	(6)
Prime first lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	1	1	1	2
Alt-A first lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	(7)	9	(7)	37
Option ARM | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	22	25	(39)	94
First mortgage, subprime | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	31	9	65	33
Total first lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	47	44	20	166
Close ended second lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	0	(1)	19	1
HELOCs | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	(28)	2	(44)	21
Second lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	(28)	1	(25)	22
U.S. RMBS | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	19	45	(5)	188
TruPS | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	0	2	(1)	(4)
Other structured finance | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	(12)	1	(33)	2
US Public Finance | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	47	2	121	47
Public finance Non-U.S. | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	$ 12	$ 38	$ 13	$ 233