Outstanding Exposure - Debt Service Outstanding (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	$ 538,642	$ 559,470
Net Debt Service Outstanding	516,399	536,341
Public Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	496,630	515,494
Net Debt Service Outstanding	476,362	494,426
Structured Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	42,012	43,976
Net Debt Service Outstanding	$ 40,037	$ 41,915