Outstanding Exposure - Puerto Rico Gross Par and Gross Debt Service Outstanding (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	$ 363,711	$ 375,080
Puerto Rico [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Par Outstanding	4,698	4,971
Gross Debt Service Outstanding	$ 7,316	$ 8,035