Reserves for Expected Costs of Liquidation and Residual Wind-Down Claims and Costs - Summary of Activity in Reserves for Expected Costs of Liquidation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Restructuring Cost and Reserve [Line Items]
Beginning Balance	$ 38,087	$ 18,903	$ 23,399
Plus additions to reserves	9,511	33,948	12,123
Less liquidation costs incurred:
Less funds returned to DIP Lenders			(6,000)
Ending Balance	37,485	38,087	18,903
Liquidation Basis of Accounting [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	38,087
Less liquidation costs incurred:
Ending Balance	37,485	38,087
Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(5,238)	(10,093)	(5,589)
Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(4,530)	(4,404)	(4,716)
Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(345)	(267)	(314)
Reserve for Expected Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	25,204	9,851	16,727
Plus additions to reserves	4,122	25,351	5,325
Less liquidation costs incurred:
Less funds returned to DIP Lenders			(6,000)
Ending Balance	23,379	25,204	9,851
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(3,125)	(7,424)	(3,295)
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(2,695)	(2,523)	(2,848)
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(127)	(51)	(58)
Reserve for Expected Reporting Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	12,739	8,827	6,379
Plus additions to reserves	5,389	8,597	6,798
Less liquidation costs incurred:
Ending Balance	13,996	12,739	8,827
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(2,113)	(2,669)	(2,294)
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(1,801)	(1,800)	(1,800)
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(218)	(216)	(256)
Reserve for Indenture Trustee/Fiscal and Paying Agent Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	144	225	293
Less liquidation costs incurred:
Ending Balance	110	144	225
Reserve for Indenture Trustee/Fiscal and Paying Agent Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	$ (34)	$ (81)	$ (68)