Insurance Company Regulatory Requirements - Dividends and Surplus Notes By Insurance Company Subsidiaries (Details) (Affiliated Entity [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Assured Guaranty LTD [Member] | Assured Guaranty Re [Member]
Statutory Accounting Practices [Line Items]
Dividends paid	$ 50	$ 62
AGMH [Member] | AGM [Member]
Statutory Accounting Practices [Line Items]
Dividends paid	66	0
Repayment of surplus notes	25	25
AGUS [Member] | AGC [Member]
Statutory Accounting Practices [Line Items]
Dividends paid	$ 20	$ 0