Insurance Company Regulatory Requirements - Dividends and Surplus Notes By Insurance Company Subsidiaries (Details) - Affiliated Entity [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Municipal Assurance Corp Holdings [Member] | MAC [Member]
Statutory Accounting Practices [Line Items]
Issuance of surplus notes	$ 0	$ 0	$ (300)
AGM [Member] | MAC [Member]
Statutory Accounting Practices [Line Items]
Issuance of surplus notes	0	0	(100)
Assured Guaranty LTD [Member] | Assured Guaranty Re [Member]
Statutory Accounting Practices [Line Items]
Dividends paid	150	82	144
AGMH [Member] | AGM [Member]
Statutory Accounting Practices [Line Items]
Dividends paid	215	160	163
Repayment of surplus notes	25	50	50
AGUS [Member] | AGC [Member]
Statutory Accounting Practices [Line Items]
Dividends paid	$ 90	$ 69	$ 67