Business Developments And Risks And Uncertainties (Narrative) (Detail) $ in Millions				3 Months Ended
	Mar. 15, 2022 USD ($)	Jan. 31, 2022 USD ($)	Jan. 01, 2022 USD ($)	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($) segments
Business Acquisition [Line Items]
Number of operating segments | segments					3
GO PSA [Member]
Business Acquisition [Line Items]
Proceeds from GO PSA	$ 1,000
Puerto Rico Electric Power Authority [Member]
Business Acquisition [Line Items]
Bankruptcy claims sold		$ 231
Percentage rate of claim which reduces potential volatility and ongoing risk					35.00%
National Public Finance Guarantee Corporation [Member] | GO PSA [Member]
Business Acquisition [Line Items]
Acceleration and commutation payment					$ 277
Subsequent Event [Member] | National Public Finance Guarantee Corporation [Member]
Business Acquisition [Line Items]
Bonds issued				$ 1,200
Subsequent Event [Member] | National Public Finance Guarantee Corporation [Member] | Puerto Rico Highway and Transportation Authority [Member]
Business Acquisition [Line Items]
Cash				264
Contingent value instrument				$ 2,200
Maximum [Member] | National Public Finance Guarantee Corporation [Member] | GO and PBA [Member]
Business Acquisition [Line Items]
Outstanding bonds					0
Gross par outstanding					0
Minimum [Member] | National Public Finance Guarantee Corporation [Member] | GO and PBA [Member]
Business Acquisition [Line Items]
Outstanding bonds					495
Gross par outstanding					380
Puerto Rico [Member]
Business Acquisition [Line Items]
Claims payments			$ 47
Outstanding bonds					$ 2,100