Insurance In Force (Summary Of Company's Reinsurance Agreements For U.S. Public Finance And Structured Finance And International Insurance Operations) (Detail) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Ceded Par Outstanding		$ 1,480	$ 1,800
Letters of Credit/Trust Accounts		21
Reinsurance Recoverable/ (Payable)	[1]	(38)
Assured Guaranty Corp [Member]
Ceded Par Outstanding		620
Letters of Credit/Trust Accounts		0
Reinsurance Recoverable/ (Payable)	[1]	(37)
Assured Guaranty Re Ltd [Member]
Ceded Par Outstanding	[2]	584
Letters of Credit/Trust Accounts	[2]	21
Reinsurance Recoverable/ (Payable)	[1],[2]	0
Overseas Private Investment Corporation [Member]
Ceded Par Outstanding		221
Letters of Credit/Trust Accounts		0
Reinsurance Recoverable/ (Payable)	[1]	0
Others [Member]
Ceded Par Outstanding	[2]	55
Letters of Credit/Trust Accounts	[2]	0
Reinsurance Recoverable/ (Payable)	[1],[2]	$ (1)

[1] Total reinsurance recoverable/(payable) is primarily related to recoverables on unpaid losses net of (payables) on salvage received.

[2] Represents a withdrawal of ratings.