Outstanding Insurance Exposure - Debt Service Outstanding (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	$ 365,435	$ 375,776
Net Debt Service Outstanding	364,507	374,130
Public finance
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	354,548	363,497
Net Debt Service Outstanding	354,122	362,361
Structured finance
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	10,887	12,279
Net Debt Service Outstanding	$ 10,385	$ 11,769