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, 2019	Dec. 31, 2018
Ceded Par Outstanding		$ 1,761	$ 2,200
Letters of Credit/Trust Accounts		32
Assured Guaranty Corp [Member]
Ceded Par Outstanding		756
Reinsurance Recoverable	[1]	(4)
Assured Guaranty Re Ltd [Member]
Ceded Par Outstanding		725
Letters of Credit/Trust Accounts		29
Reinsurance Recoverable	[1]	4
Overseas Private Investment Corporation [Member]
Ceded Par Outstanding		220
Others [Member]
Ceded Par Outstanding		60
Letters of Credit/Trust Accounts		$ 3

[1] Total reinsurance recoverable is primarily related to recoverables on unpaid losses.