Financial Guaranty Insurance Losses (Details 5) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Guarantor Obligations [Line Items]
Subtotal	$ 84	$ 122	$ 29	$ 372
Effect of consolidating FG VIEs	(22)	(4)	(15)	(12)
Loss and LAE	62	118	14	360
Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	84	128	29	378
Other
Guarantor Obligations [Line Items]
Subtotal	0	(6)	0	(6)
Prime first lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	0	1	0	1
Alt-A first lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	(9)	29	0	28
First mortgage, option adjustable rate mortgage | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	22	17	(61)	69
First mortgage, subprime | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	23	16	34	24
Total first lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	36	63	(27)	122
Close ended second lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	(1)	3	19	2
HELOCs | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	(19)	4	(16)	19
Second lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	(20)	7	3	21
U.S. RMBS | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	16	70	(24)	143
TruPS | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	(1)	(2)	(1)	(6)
Other structured finance | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	(9)	29	(21)	1
US Public Finance | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	78	26	74	45
Public finance Non-U.S. | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal	$ 0	$ 5	$ 1	$ 195