Financial Guaranty Insurance Losses - Other (Details) (USD $)			3 Months Ended		3 Months Ended
	Dec. 31, 2013	Mar. 31, 2014 AGM	Mar. 31, 2014 Variable rate demand obligations	Mar. 31, 2014 Variable rate demand obligations AGM and AGC	Mar. 31, 2014 Minimum Variable rate demand obligations	Mar. 31, 2014 Maximum Variable rate demand obligations	Mar. 31, 2014 Cash Minimum	Mar. 31, 2014 Asset-backed securities Maximum
Guarantor Obligations [Line Items]
Maximum possible estimated termination payment on swap obligations after taking account the rating downgrade in January 2013		$ 104,000,000
Maximum possible estimated termination payment on swap obligations after taking account the possibility of further rating downgrades		290,000,000
Rate basis for bank bond rate			prime rate
Bank bond rate (as a percent)					2.00%	3.00%
Bank bond capped rate (as a percent)						25.00%
Threshold period of bonds held by bank for right of accelerated repayment (in days)					90 days	180 days
Financial guaranty insurance contracts principal amount insured				7,000,000,000
Financial Guaranty Insurance Contracts, Principal Amount BBB- or below				400,000,000
Collateralization as a Percentage of GIC Balance							100.00%	108.00%
Guaranteed Investment Contract, Aggregate Accreted Balance	2,600,000,000
Assets of GIC Issuers, Aggregate Accreted Principal	3,900,000,000
Assets of GIC Issuers, Aggregate Market Value	$ 3,700,000,000