Reserves for Expected Costs of Liquidation and Residual Wind-Down Claims - Summary of Activity in Reserves for Expected Costs of Liquidation (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Reserve for Expected Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Plus (Less) additions to (reductions in) reserves	$ 9,000	$ (3,800)	$ 5,200
Reserve for Expected Reporting Costs [Member]
Restructuring Cost and Reserve [Line Items]
Plus (Less) additions to (reductions in) reserves	400	(4,100)	12,300
Liquidation Basis of Accounting [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	36,486	61,513	76,111
Plus (Less) additions to (reductions in) reserves	9,375	(7,910)	17,488
Less liquidation costs incurred:
Ending Balance	31,278	36,486	61,513
Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(8,739)	(11,020)	(25,487)
Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(5,438)	(5,722)	(6,205)
Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(406)	(375)	(394)
Liquidation Basis of Accounting [Member] | Reserve for Expected Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	22,529	38,043	56,815
Plus (Less) additions to (reductions in) reserves	8,962	(3,843)	5,195
Less liquidation costs incurred:
Ending Balance	21,089	22,529	38,043
Liquidation Basis of Accounting [Member] | Reserve for Expected Wind-Down Costs [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(6,834)	(7,736)	(19,712)
Liquidation Basis of Accounting [Member] | Reserve for Expected Wind-Down Costs [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(3,537)	(3,888)	(4,191)
Liquidation Basis of Accounting [Member] | Reserve for Expected Wind-Down Costs [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(31)	(47)	(64)
Liquidation Basis of Accounting [Member] | Reserve for Expected Reporting Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	12,235	20,442	13,320
Plus (Less) additions to (reductions in) reserves	413	(4,067)	12,293
Less liquidation costs incurred:
Ending Balance	8,602	12,235	20,442
Liquidation Basis of Accounting [Member] | Reserve for Expected Reporting Costs [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(1,870)	(2,013)	(2,985)
Liquidation Basis of Accounting [Member] | Reserve for Expected Reporting Costs [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(1,801)	(1,799)	(1,866)
Liquidation Basis of Accounting [Member] | Reserve for Expected Reporting Costs [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(375)	(328)	(320)
Liquidation Basis of Accounting [Member] | Reserve for Indenture Trustee/Fiscal and Paying Agent Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance				647
Less liquidation costs incurred:
Ending Balance	364	464	499	647
Liquidation Basis of Accounting [Member] | Reserve for Indenture Trustee/Fiscal and Paying Agent Costs [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(100)	(35)	(148)
Liquidation Basis of Accounting [Member] | Reserve for Avoidance Action Defense Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance				1,280
Less liquidation costs incurred:
Ending Balance			898	1,280
Liquidation Basis of Accounting [Member] | Reserve for Avoidance Action Defense Costs [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred		(898)	(382)
Liquidation Basis of Accounting [Member] | Reserve for Residual Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance				4,049
Less liquidation costs incurred:
Ending Balance	1,223	1,258	1,631	4,049
Liquidation Basis of Accounting [Member] | Reserve for Residual Wind-Down Costs [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(35)	(373)	(2,408)
Liquidation Basis of Accounting [Member] | Reserve for Residual Wind-Down Costs [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred			$ (10)