Reinsurance and Other Monoline Exposures (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Feb. 14, 2013 AG Re	Dec. 31, 2012 AG Re	Dec. 31, 2012 AGC
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Fair market value of company's pledged securities	$ 660				$ 780				$ 660		$ 780				$ 27	$ 328	$ 147
Additional ceding commission																8
Commutation gains (losses)									82		32		50
Premiums Written:
Direct									244		190		343
Assumed									9	[1]	(63)	[1]	(121)	[1]
Ceded									51	[2]	4	[2]	101	[2]
Net									304		131		323
Commutations									109		(20)		20
Increase (Decrease) in Net Par Due to Commutations									19,173		(780)		12,373
Premiums Earned:
Direct									936		997		1,243
Assumed									50		46		73
Ceded									(133)		(123)		(129)
Net earned premiums	218	222	219	194	225	211	230	254	853	[3]	920	[3]	1,187	[3]
Loss and LAE:
Direct									655		578		399
Assumed									(4)		4		74
Ceded									(128)		(120)		(61)
Loss and LAE	$ 64	$ 90	$ 122	$ 247	$ 149	$ 215	$ 124	$ (26)	$ 523		$ 462		$ 412

[1] Negative assumed premiums written were due to cancellations and changes in expected Debt Service schedules.

[2] Positive ceded premiums written were due to commutations and changes in expected Debt Service schedules.

[3] Excludes $153 million, $75 million and $48 million for the year ended December 31, 2012, 2011 and 2010, respectively, related to consolidated FG VIEs.