Financial Guaranty Insurance Premiums - Selected Information for Policies Paid in Installments (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2015		Dec. 31, 2014	Sep. 30, 2014	[1]	Dec. 31, 2013
Financial Guarantee Insurance Premiums [Line Items]
Premiums receivable, net of commission payable	$ 676	[1]	$ 729	$ 801		$ 876
Policies Paid in Installments [Member]
Financial Guarantee Insurance Premiums [Line Items]
Premiums receivable, net of commission payable	676		729
Gross deferred premium revenue	$ 1,250		$ 1,370
Weighted-average risk-free rate used to discount premiums	3.40%		3.50%
Weighted-average period of premiums receivable (in years)	9 years 3 months 24 days		9 years 4 months 24 days

[1] Excludes $23 million and $18 million as of September 30, 2015 and September 30, 2014, respectively, related to consolidated FG VIEs.