Financial Guaranty Insurance - Selected Information for Policies Paid In Installments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financial Guarantee Insurance Premiums [Line Items]
Premiums receivable, net of commission payable	$ 693	$ 729	$ 876	$ 1,005
Financial Guarantee Policies Paid in Installments [Member]
Financial Guarantee Insurance Premiums [Line Items]
Premiums receivable, net of commission payable	693	729
Gross deferred premium revenue	$ 1,240	$ 1,370
Weighted-average risk-free rate used to discount premiums (as a percent)	3.10%	3.50%
Weighted-average period of premiums receivable (in years)	9 years 4 months 24 days	9 years 4 months 24 days