Outstanding Exposure - Puerto Rico Gross Par and Gross Debt Service Outstanding (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Schedule of Insured Financial Obligations [Line Items]
Exposure to Puerto Rico	$ 248,626	$ 249,535
Gross	395,350	398,037
Puerto Rico
Schedule of Insured Financial Obligations [Line Items]
Exposure to Puerto Rico	976	1,120
Gross	$ 1,270	$ 1,526