Insurance Company Regulatory Requirements - Dividends and Surplus Notes By Insurance Company Subsidiaries (Details) (Affiliated Entity [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Municipal Assurance Corp Holdings [Member] | MAC [Member]
Statutory Accounting Practices [Line Items]
Issuance of surplus notes	$ 0	$ (300)	$ 0
AGM [Member] | MAC [Member]
Statutory Accounting Practices [Line Items]
Issuance of surplus notes	0	(100)	0
Assured Guaranty LTD [Member] | Assured Guaranty Re [Member]
Statutory Accounting Practices [Line Items]
Dividends paid	82	144	151
AGMH [Member] | AGM [Member]
Statutory Accounting Practices [Line Items]
Dividends paid	160	163	30
Repayment of surplus notes	50	50	50
AGUS [Member] | AGC [Member]
Statutory Accounting Practices [Line Items]
Dividends paid	$ 69	$ 67	$ 55