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	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Restructuring Cost and Reserve [Line Items]
Beginning Balance	$ 21,882	$ 30,118	$ 24,611	$ 31,278
Plus additions to reserves	5,315	7,967	5,043	10,298
Less liquidation costs incurred:
Ending Balance	24,588	32,902	24,588	32,902
Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(1,336)	(2,759)	(2,471)	(4,879)
Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(1,233)	(1,509)	(2,456)	(2,794)
Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(40)	(915)	(139)	(1,001)
Reserve for Expected Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	15,027	20,344	16,727	21,089
Plus additions to reserves	1,666	5,748	1,356	7,195
Less liquidation costs incurred:
Ending Balance	15,298	22,176	15,298	22,176
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(618)	(2,017)	(1,234)	(3,381)
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(763)	(1,041)	(1,519)	(1,859)
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(14)	(858)	(32)	(868)
Reserve for Expected Reporting Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	5,368	8,206	6,379	8,602
Plus additions to reserves	3,649	2,219	3,687	3,103
Less liquidation costs incurred:
Ending Balance	7,824	9,178	7,824	9,178
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(717)	(740)	(1,235)	(1,494)
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(450)	(450)	(900)	(900)
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(26)	(57)	(107)	(133)
Reserve for Indenture Trustee/Fiscal and Paying Agent Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	276	347	293	364
Less liquidation costs incurred:
Ending Balance	256	329	256	329
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	(20)	(18)	(37)	(35)
Reserve for Residual Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	1,211	1,221	1,212	1,223
Less liquidation costs incurred:
Ending Balance	1,210	1,219	1,210	1,219
Reserve for Residual Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	$ (1)	$ (2)	$ (2)	$ (4)