Certain Summary Information with Respect to Trapeza Collateralized Debt Obligations and Underlying Issuers (Detail) (Collateralized Debt Obligations)	9 Months Ended	12 Months Ended
	Sep. 30, 2012 Contract	Dec. 31, 2011 Contract
Collateralized Debt Obligations
Current number of performing and non-performing issuers, Performing	36	36
Current number of performing and non-performing issuers, Deferring interest	10	10
Current number of performing and non-performing issuers, Defaulted	9	9
Actual deferrals and defaults as a percentage of the original collateral, Deferral	13.60%	15.40%
Actual deferrals and defaults as a percentage of the original collateral, Defaults	14.10%	12.90%
Expected deferrals and defaults as a percentage of the remaining performing collateral, Expected new deferrals	0.00%	0.00%
Expected deferrals and defaults as a percentage of the remaining performing collateral, Expected new defaults	1.80%	8.20%
Subordination level of the tranche held by the registrant as a percentage of the remaining performing collateral	11.20%	11.30%
Subordination level of the tranche held by the registrant plus all superior tranche levels as a percentage of the remaining performing collateral	112.60%	108.10%
External credit ratings (Moody's / Fitch)	Ca / C	Ca / C