Financial Guaranty Insurance Premiums - Selected Information for Policies Paid in Installments (Details) (Policies Paid in Installments [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Policies Paid in Installments [Member]
Financial Guarantee Insurance Premiums [Line Items]
Premiums receivable, net of commission payable	$ 729	$ 876
Gross deferred premium revenue	$ 1,370	$ 1,576
Weighted-average risk-free rate used to discount premiums (as a percent)	3.50%	3.40%
Weighted-average period of premiums receivable (in years)	9 years 4 months 24 days	9 years 4 months 24 days