Outstanding Insurance Exposure - Debt Service Outstanding (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	$ 365,356	$ 375,776
Net Debt Service Outstanding	363,893	374,130
Public Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	353,984	363,497
Net Debt Service Outstanding	353,031	362,361
Structured Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	11,372	12,279
Net Debt Service Outstanding	$ 10,862	$ 11,769