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, 2021	Dec. 31, 2020
Insurance in Force		$ 78.5	$ 91.4
Gross Par Amount		41.7	49.6
U S [Member]
Insurance in Force		73.7	84.5
Non-United States [Member]
Insurance in Force		4.8	6.9
Global Public Finance [Member]
Insurance in Force		75.5	87.4
Gross Par Amount		39.7	46.7
Global Public Finance [Member] | U S [Member]
Insurance in Force		71.7	81.5
Gross Par Amount		36.5	41.9
Global Public Finance [Member] | Non-United States [Member]
Insurance in Force		3.8	5.9
Gross Par Amount		3.2	4.8
Global Structured Finance [Member]
Insurance in Force		3.0	4.0
Gross Par Amount		2.0	2.9
General Obligation [Member] | Global Public Finance [Member] | U S [Member]
Insurance in Force	[1]	22.1	25.0
Gross Par Amount	[1]	10.7	12.1
General Obligation—Lease [Member] | Global Public Finance [Member] | U S [Member]
Insurance in Force		1.7	2.4
Gross Par Amount		1.2	1.9
Municipal Utilities [Member] | Global Public Finance [Member] | U S [Member]
Insurance in Force		8.7	10.6
Gross Par Amount		6.0	7.3
Tax-Backed [Member] | Global Public Finance [Member] | U S [Member]
Insurance in Force		14.2	15.7
Gross Par Amount		6.8	7.9
Transportation [Member] | Non-United States [Member]
Insurance in Force		1.2	2.1
Gross Par Amount		1.0	1.8
Transportation [Member] | Global Public Finance [Member] | U S [Member]
Insurance in Force		7.7	9.2
Gross Par Amount		2.6	3.0
Higher Education [Member] | Global Public Finance [Member] | U S [Member]
Insurance in Force		1.3	1.5
Gross Par Amount		1.0	1.1
Health Care [Member] | Global Public Finance [Member] | U S [Member]
Insurance in Force		1.0	1.2
Gross Par Amount		0.7	0.8
Military Housing [Member] | Global Public Finance [Member] | U S [Member]
Insurance in Force		14.3	14.8
Gross Par Amount		6.9	7.0
Investor-Owned Utilities [Member] | Global Public Finance [Member] | U S [Member]
Insurance in Force	[2]	0.6	0.9
Gross Par Amount	[2]	0.5	0.6
Municipal Housing [Member] | Global Public Finance [Member] | U S [Member]
Insurance in Force		0.0	0.1
Gross Par Amount		0.0	0.1
Other Public Finance [Member] | Non-United States [Member]
Insurance in Force	[3]	0.1	0.1
Gross Par Amount	[3]	0.1	0.1
Other Public Finance [Member] | Global Public Finance [Member] | U S [Member]
Insurance in Force	[4]	0.1	0.1
Gross Par Amount	[4]	0.1	0.1
International Utilities [Member] | Non-United States [Member]
Insurance in Force		0.5	0.9
Gross Par Amount		0.5	0.8
Sovereign Related And Sub-Sovereign [Member] | Non-United States [Member]
Insurance in Force	[5]	2.0	2.8
Gross Par Amount	[5]	1.6	2.1
Collateralized Debt Obligations [Member] | Global Structured Finance [Member]
Insurance in Force		0.3	0.4
Gross Par Amount		0.2	0.3
Residential Mortgage Backed Securities [Member] | Global Structured Finance [Member]
Insurance in Force		1.5	2.0
Gross Par Amount		1.0	1.5
Commercial Mortgage Backed Securities [Member] | Global Structured Finance [Member]
Insurance in Force		0.4	0.5
Gross Par Amount		0.2	0.2
Consumer Asset Backed [Member] | Global Structured Finance [Member]
Insurance in Force		0.2	0.3
Gross Par Amount		0.2	0.3
Corporate Asset Backed [Member] | Global Structured Finance [Member]
Insurance in Force	[6]	0.6	0.8
Gross Par Amount	[6]	$ 0.4	$ 0.6

[1] 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.

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

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

[4] Includes stadium related financings and certain non-profit enterprises.

[5] 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.

[6] As of December 31, 2020, all remaining insurance in force and gross par relating to structured insurance securitizations was terminated.