Insurance In Force (Schedule Of Insurance In Force By Type Of Bond, Excluding Transactions Guaranteed By MBIA Corp. On Behalf Of Various Investment Management Services And Other Affiliated Companies) (Detail) - USD ($) $ in Billions		Dec. 31, 2023	Dec. 31, 2022
Insurance in Force		$ 60.9	$ 68.0
Gross Par Amount		31.2	35.1
U S [Member]
Insurance in Force		58.4	65.1
Non-United States [Member]
Insurance in Force		2.5	2.9
Transportation [Member] | Non-United States [Member]
Insurance in Force		0.4	0.5
Gross Par Amount		0.4	0.4
Other Public Finance [Member] | Non-United States [Member]
Insurance in Force	[1]	0.1	0.1
Gross Par Amount	[1]	0.1	0.1
Sovereign Related And Sub-Sovereign [Member] | Non-United States [Member]
Insurance in Force	[2]	1.3	1.5
Gross Par Amount	[2]	1.0	1.2
Global Public Finance [Member]
Insurance in Force		58.9	65.5
Gross Par Amount		29.8	33.4
Global Public Finance [Member] | U S [Member]
Insurance in Force		57.1	63.4
Gross Par Amount		28.3	31.7
Global Public Finance [Member] | Non-United States [Member]
Insurance in Force		1.8	2.1
Gross Par Amount		1.5	1.7
Global Public Finance [Member] | General Obligation [Member] | U S [Member]
Insurance in Force	[3]	16.8	19.1
Gross Par Amount	[3]	8.0	9.1
Global Public Finance [Member] | General Obligation—Lease [Member] | U S [Member]
Insurance in Force		1.0	1.3
Gross Par Amount		0.7	1.0
Global Public Finance [Member] | Municipal Utilities [Member] | U S [Member]
Insurance in Force		6.4	7.6
Gross Par Amount		4.6	5.2
Global Public Finance [Member] | Tax-Backed [Member] | U S [Member]
Insurance in Force		11.0	12.2
Gross Par Amount		4.9	5.6
Global Public Finance [Member] | Transportation [Member] | U S [Member]
Insurance in Force		6.5	6.9
Gross Par Amount		2.1	2.2
Global Public Finance [Member] | Higher Education [Member] | U S [Member]
Insurance in Force		1.0	1.1
Gross Par Amount		0.7	0.8
Global Public Finance [Member] | Health Care [Member] | U S [Member]
Insurance in Force		0.7	0.8
Gross Par Amount		0.4	0.6
Global Public Finance [Member] | Military Housing [Member] | U S [Member]
Insurance in Force		13.2	13.8
Gross Par Amount		6.6	6.8
Global Public Finance [Member] | Investor-Owned Utilities [Member] | U S [Member]
Insurance in Force	[4]	0.4	0.5
Gross Par Amount	[4]	0.3	0.3
Global Public Finance [Member] | Other Public Finance [Member] | U S [Member]
Insurance in Force	[5]	0.1	0.1
Gross Par Amount	[5]	0.0	0.1
Global Structured Finance [Member]
Insurance in Force		2.0	2.5
Gross Par Amount		1.4	1.7
Global Structured Finance [Member] | Collateralized Debt Obligations [Member]
Insurance in Force		0.1	0.2
Gross Par Amount		0.1	0.2
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member]
Insurance in Force		0.9	1.2
Gross Par Amount		0.6	0.8
Global Structured Finance [Member] | Commercial Mortgage-Backed [Member]
Insurance in Force		0.4	0.4
Gross Par Amount		0.2	0.2
Global Structured Finance [Member] | Consumer Asset Backed [Member]
Insurance in Force		0.1	0.2
Gross Par Amount		0.1	0.1
Global Structured Finance [Member] | Corporate Asset Backed [Member]
Insurance in Force		0.5	0.5
Gross Par Amount		$ 0.4	$ 0.4

[1] Includes municipal owned entities backed by sponsoring local government, tax backed and utility transactions.

[2] Includes regions, departments or their equivalent in each jurisdiction as well as sovereign owned entities that are supported by a sovereign state, region or department.

[3] Includes general obligation unlimited and limited (property) tax bonds, general fund obligation bonds and pension obligation bonds of states, cities, counties, schools and special districts

[4] Includes investor owned utilities, industrial development and pollution control revenue bonds.

[5] Includes stadium related financings, municipal housing and certain non-profit enterprises.