Outstanding Exposure - Puerto Rico Gross Par and Gross Debt Service Outstanding (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	$ 366,788	$ 366,692
Puerto Rico
Schedule of Insured Financial Obligations [Line Items]
Gross Par Outstanding	3,629	3,789
Gross Debt Service Outstanding	$ 5,325	$ 5,674