Insurance In Force (Summary Of The Company's Reinsurance Agreements For U.S. Public Finance And Structured Finance And International Insurance Operations) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Ceded Par Outstanding	$ 4,269		$ 5,700
LOC / Trust Accounts	7
Reinsurance Recoverables	16	[1]
Reinsurance recoverables on paid losses	1
Reinsurance recoverables on unpaid losses	15
Moody's Aa3 [Member] | Assured Guaranty Corp [Member] | S&P AA+ [Member]
Ceded Par Outstanding	3,235
LOC / Trust Accounts
Reinsurance Recoverables	16	[1]
A [Member] | Assured Guaranty Re Ltd [Member] | S&P AA [Member]
Ceded Par Outstanding	542
LOC / Trust Accounts	5
Reinsurance Recoverables	0	[1]
Aaa [Member] | Overseas Private Investment Corporation [Member] | S&P AAA [Member]
Ceded Par Outstanding	320
LOC / Trust Accounts
Aaa [Member] | Export Development Canada [Member] | S&P AAA [Member]
Ceded Par Outstanding	77
LOC / Trust Accounts	1
Moody's A1 Or Above [Member] | Others [Member] | S&P A+ Or Above [Member]
Ceded Par Outstanding	95
LOC / Trust Accounts	1
Reinsurance Recoverables	$ 0	[1]

[1] reinsurance recoverable of $16 million comprised recoverables on paid and unpaid losses of $1 million and $15 million, respectively.