Commitments and Contingencies - Narrative (Details)	3 Months Ended	1 Months Ended				0 Months Ended	12 Months Ended				1 Months Ended		12 Months Ended	0 Months Ended		0 Months Ended		0 Months Ended
	Mar. 31, 2015 Lawsuit	Sep. 30, 2009 Governmental Investigations [Member] Plaintiff	Nov. 28, 2011 LBIE vs. AG Financial Products [Member] AG Financial Products Inc. [Member] Guarantee Obligations [Member] Transaction	Nov. 28, 2011 Pending Litigation LBIE vs. AG Financial Products [Member] AG Financial Products Inc. [Member] USD ($)	Sep. 25, 2013 Pending Litigation Wells Fargo Bank, N.A., Interpleader Complaint [Member] AGM [Member] USD ($)	May 28, 2014 Pending Litigation Houston Casualty Company Europe Vs Assured Guaranty [Member] Radian [Member] EUR (€)	Dec. 31, 2008 Pending Litigation MDL 1950 [Member] Lawsuit	Dec. 31, 2008 Pending Litigation MDL 1950 [Member] AGMH [Member] Lawsuit	Dec. 31, 2008 Pending Litigation MDL 1950 [Member] AGM and AGMH [Member] Lawsuit	Dec. 31, 2008 Pending Litigation Non-class Action Cases Consolidated with MDL 1950 for Pretrial Proceedings [Member] AGM and AGMH [Member] Proceedings Related to Former Financial Products Business [Member] Lawsuit	May 31, 2010 Pending Litigation Non-class Action Cases Consolidated with MDL 1950 for Pretrial Proceedings [Member] AGM and AGUS [Member] Proceedings Related to Former Financial Products Business [Member] Lawsuit	Apr. 30, 2010 Pending Litigation Non-class Action Cases Consolidated with MDL 1950 for Pretrial Proceedings [Member] AGM and AGUS [Member] Proceedings Related to Former Financial Products Business [Member] Lawsuit	Dec. 31, 2009 Pending Litigation Non-class Action Cases Consolidated with MDL 1950 for Pretrial Proceedings [Member] AGM and AGUS [Member] Proceedings Related to Former Financial Products Business [Member] Lawsuit	Nov. 19, 2012 Pending Litigation LBHI and LBSF vs CPT 283, FSA and AGM [Member] AGM [Member] USD ($)	Nov. 19, 2012 Pending Litigation LBHI and LBSF vs CPT 283, FSA and AGM [Member] AGM [Member] USD ($)	Nov. 19, 2012 Pending Litigation LBHI and LBSF vs CPT 207, FSA and AGM [Member] AGM [Member] USD ($)	Nov. 19, 2012 Pending Litigation LBHI and LBSF vs CPT 207, FSA and AGM [Member] AGM [Member] USD ($)	Jan. 30, 2015 Settled Litigation [Member] LBHI and LBSF vs CPT 207, FSA and AGM [Member] AGM [Member] USD ($)	Nov. 28, 2011 Positive Outcome of Litigation [Member] LBIE vs. AG Financial Products [Member] Lehman Brothers International (Europe) [Member] Transaction	Apr. 10, 2015 Minimum [Member] Positive Outcome of Litigation [Member] Subsequent Event [Member] LBIE vs. AG Financial Products [Member] Lehman Brothers International (Europe) [Member] USD ($)	Apr. 10, 2015 Maximum [Member] Positive Outcome of Litigation [Member] Subsequent Event [Member] LBIE vs. AG Financial Products [Member] Lehman Brothers International (Europe) [Member] USD ($)
Commitments and Contingencies Legal Proceedings
Minimum number of proceedings for recoveries to have potential material impact	1
Number of credit derivative transactions for which termination payment is alleged to be improperly calculated			9
Gain contingency, number of credit derivative transactions with improperly calculated payments																			28
Gain contingency, unrecorded amount																				$ 200,000,000	$ 500,000,000
Termination payments which LBIE owes to AG Financial Products as per calculation of AG Financial Products				30,000,000											43,800,000		492,555
Loss Contingency, Damages Sought, Value						14,000,000								67,300,000		1,500,000
Litigation Settlement, Amount																		20,000,000
Termination payments which AG Financial Products owes to LBIE as per calculation of LBIE				1,400,000,000
Increase in losses as a result of an adverse outcome, minimum					10,000,000
Increase in losses as a result of an adverse outcome, maximum					$ 20,000,000
Number of putative class action lawsuits filed in federal court							9	4	5	5	5		6
Number of plaintiffs filing consolidated complaints		4
Number of non-class action lawsuits for which dismissal was denied												11