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, 2022	Dec. 31, 2021
Insurance in Force		$ 68.0	$ 78.5
Gross Par Amount		35.1	41.7
U S [Member]
Insurance in Force		65.1	73.7
Non-United States [Member]
Insurance in Force		2.9	4.8
Transportation [Member] | Non-United States [Member]
Insurance in Force		0.5	1.2
Gross Par Amount		0.4	1.0
Other Public Finance [Member] | Non-United States [Member]
Insurance in Force	[1]	0.1	0.1
Gross Par Amount	[1]	0.1	0.1
International Utilities [Member] | Non-United States [Member]
Insurance in Force		0.0	0.5
Gross Par Amount		0.0	0.5
Sovereign Related And Sub-Sovereign [Member] | Non-United States [Member]
Insurance in Force	[2]	1.5	2.0
Gross Par Amount	[2]	1.2	1.6
Global Public Finance [Member]
Insurance in Force		65.5	75.5
Gross Par Amount		33.4	39.7
Global Public Finance [Member] | U S [Member]
Insurance in Force		63.4	71.7
Gross Par Amount		31.7	36.5
Global Public Finance [Member] | Non-United States [Member]
Insurance in Force		2.1	3.8
Gross Par Amount		1.7	3.2
Global Public Finance [Member] | General Obligation [Member] | U S [Member]
Insurance in Force	[3]	19.1	22.1
Gross Par Amount	[3]	9.1	10.7
Global Public Finance [Member] | General Obligation—Lease [Member] | U S [Member]
Insurance in Force		1.3	1.7
Gross Par Amount		1.0	1.2
Global Public Finance [Member] | Municipal Utilities [Member] | U S [Member]
Insurance in Force		7.6	8.7
Gross Par Amount		5.2	6.0
Global Public Finance [Member] | Tax-Backed [Member] | U S [Member]
Insurance in Force		12.2	14.2
Gross Par Amount		5.6	6.8
Global Public Finance [Member] | Transportation [Member] | U S [Member]
Insurance in Force		6.9	7.7
Gross Par Amount		2.2	2.6
Global Public Finance [Member] | Higher Education [Member] | U S [Member]
Insurance in Force		1.1	1.3
Gross Par Amount		0.8	1.0
Global Public Finance [Member] | Health Care [Member] | U S [Member]
Insurance in Force		0.8	1.0
Gross Par Amount		0.6	0.7
Global Public Finance [Member] | Military Housing [Member] | U S [Member]
Insurance in Force		13.8	14.3
Gross Par Amount		6.8	6.9
Global Public Finance [Member] | Investor-Owned Utilities [Member] | U S [Member]
Insurance in Force	[4]	0.5	0.6
Gross Par Amount	[4]	0.3	0.5
Global Public Finance [Member] | Other Public Finance [Member] | U S [Member]
Insurance in Force	[5]	0.1	0.1
Gross Par Amount	[5]	0.1	0.1
Global Structured Finance [Member]
Insurance in Force		2.5	3.0
Gross Par Amount		1.7	2.0
Global Structured Finance [Member] | Collateralized Debt Obligations [Member]
Insurance in Force		0.2	0.3
Gross Par Amount		0.2	0.2
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member]
Insurance in Force		1.2	1.5
Gross Par Amount		0.8	1.0
Global Structured Finance [Member] | Commercial Mortgage Backed Securities [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		0.2	0.2
Gross Par Amount		0.1	0.2
Global Structured Finance [Member] | Corporate Asset Backed [Member]
Insurance in Force		0.5	0.6
Gross Par Amount		$ 0.4	$ 0.4

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