Financial Guaranty Insurance Losses - Balance Sheet Classification of Net Expected Recoveries for Breaches of R&W Insurance Contracts (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Salvage and subrogation recoverable, net [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net expected recoveries for breaches of R&W insurance contracts	$ 20	[1]	$ 73	[1]
Salvage and subrogation recoverable, net [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net expected recoveries for breaches of R&W insurance contracts	0		(49)
Loss and LAE reserve, net [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net expected recoveries for breaches of R&W insurance contracts	177	[1]	339	[1]
Loss and LAE reserve, net [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net expected recoveries for breaches of R&W insurance contracts	(8)		(24)
Financial Guarantee Insurance Product Line [Member] | Salvage and subrogation recoverable, net [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net expected recoveries for breaches of R&W insurance contracts	20		122
Financial Guarantee Insurance Product Line [Member] | Loss and LAE reserve, net [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net expected recoveries for breaches of R&W insurance contracts	$ 185		$ 363

[1] The remaining benefit for R&W is either recorded at fair value in FG VIE assets, or not recorded on the balance sheet until the total loss, net of R&W, exceeds unearned premium reserve.