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, 2016		Dec. 31, 2015
Aggregate Amount Of Insured Par Outstanding Ceded To Reinsurers		$ 4,162	[1]	$ 5,300
Reinsurance Recoverables Secured By Letters Of Credit Or Trust Amount		29
Reinsurance Recoverable	[2]	6
MBIA UK [Member]
Aggregate Amount Of Insured Par Outstanding Ceded To Reinsurers		170
Assured Guaranty Corp [Member]
Aggregate Amount Of Insured Par Outstanding Ceded To Reinsurers	[1]	1,391
Reinsurance Recoverable	[2]	6
Assured Guaranty Re Ltd [Member]
Aggregate Amount Of Insured Par Outstanding Ceded To Reinsurers	[1]	2,402
Reinsurance Recoverables Secured By Letters Of Credit Or Trust Amount		26
Overseas Private Investment Corporation [Member]
Aggregate Amount Of Insured Par Outstanding Ceded To Reinsurers	[1]	264
Others [Member]
Aggregate Amount Of Insured Par Outstanding Ceded To Reinsurers	[1]	105
Reinsurance Recoverables Secured By Letters Of Credit Or Trust Amount		$ 3

[1] Includes $170 million in ceded par outstanding related to MBIA UK.

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