Outstanding Exposure - Debt Service Outstanding (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	$ 619,932	$ 646,722
Net Debt Service Outstanding	584,659	609,622
Public Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	565,386	587,245
Net Debt Service Outstanding	533,359	553,612
Structured Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Debt Service Outstanding	54,546	59,477
Net Debt Service Outstanding	$ 51,300	$ 56,010