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	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Beginning Balance	$ 41,897	$ 22,515	$ 38,087	$ 18,903
Plus addition to (reduction in) reserves	855	6,148	9,434	15,668
Less liquidation costs incurred:
Ending Balance	40,559	23,421	40,559	23,421
Liquidation Basis of Accounting [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance			38,087
Less liquidation costs incurred:
Ending Balance	40,559		40,559
Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(1,016)	(4,079)	(3,255)	(7,661)
Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(1,057)	(1,078)	(3,445)	(3,313)
Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(120)	(85)	(262)	(176)
Reserve for Expected Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	26,927	11,038	25,204	9,851
Plus addition to (reduction in) reserves	(479)	6,307	3,944	11,037
Less liquidation costs incurred:
Ending Balance	25,305	13,305	25,305	13,305
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(488)	(3,432)	(1,655)	(5,643)
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(616)	(598)	(2,082)	(1,903)
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(39)	(10)	(106)	(37)
Reserve for Expected Reporting Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	14,847	11,282	12,739	8,827
Plus addition to (reduction in) reserves	1,334	(159)	5,490	4,631
Less liquidation costs incurred:
Ending Balance	15,121	9,951	15,121	9,951
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(528)	(647)	(1,600)	(2,018)
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(451)	(450)	(1,352)	(1,350)
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(81)	(75)	(156)	(139)
Reserve for Indenture Trustee/Fiscal and Paying Agent Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	123	195	144	225
Less liquidation costs incurred:
Ending Balance	133	165	133	165
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	$ 10	$ (30)	$ (11)	$ (60)