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, 2018	Mar. 31, 2017	Mar. 31, 2016
Restructuring Cost and Reserve [Line Items]
Beginning Balance	$ 18,903	$ 23,399	$ 30,055
Plus additions to reserves	33,948	12,123	7,711
Less liquidation costs incurred:
Less funds returned to DIP Lenders		(6,000)
Ending Balance	38,087	18,903	23,399
Liquidation Basis of Accounting [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	18,903
Less liquidation costs incurred:
Ending Balance	38,087	18,903
Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(10,093)	(5,589)	(7,916)
Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(4,404)	(4,716)	(5,309)
Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(267)	(314)	(1,142)
Reserve for Expected Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	9,851	16,727	21,089
Plus additions to reserves	25,351	5,325	5,592
Less liquidation costs incurred:
Less funds returned to DIP Lenders		(6,000)
Ending Balance	25,204	9,851	16,727
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(7,424)	(3,295)	(5,625)
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(2,523)	(2,848)	(3,438)
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(51)	(58)	(891)
Reserve for Expected Reporting Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	8,827	6,379	8,602
Plus additions to reserves	8,597	6,798	2,119
Less liquidation costs incurred:
Ending Balance	12,739	8,827	6,379
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(2,669)	(2,294)	(2,291)
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(1,800)	(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	(216)	(256)	(251)
Reserve for Indenture Trustee/Fiscal and Paying Agent Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	225	293	364
Less liquidation costs incurred:
Ending Balance	144	225	293
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	$ (81)	$ (68)	$ (71)