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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Restructuring Cost and Reserve [Line Items]
Beginning Balance	$ 30,118	$ 34,680	$ 31,278	$ 36,486
Plus additions to (reductions in) reserves	7,967	2,291	10,298	4,135
Less liquidation costs incurred (net of reversals):
Ending Balance	32,902	33,347	32,902	33,347
Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred (net of reversals):
Liquidation costs incurred (net of reversals)	(2,759)	(2,195)	(4,879)	(4,326)
Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred (net of reversals):
Liquidation costs incurred (net of reversals)	(1,509)	(1,400)	(2,794)	(2,788)
Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred (net of reversals):
Liquidation costs incurred (net of reversals)	(915)	(29)	(1,001)	(160)
Reserve for Expected Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	20,344	22,513	21,089	22,529
Plus additions to (reductions in) reserves	5,748	2,240	7,195	4,677
Less liquidation costs incurred (net of reversals):
Ending Balance	22,176	22,042	22,176	22,042
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred (net of reversals):
Liquidation costs incurred (net of reversals)	(2,017)	(1,801)	(3,381)	(3,327)
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred (net of reversals):
Liquidation costs incurred (net of reversals)	(1,041)	(912)	(1,859)	(1,829)
Reserve for Expected Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred (net of reversals):
Liquidation costs incurred (net of reversals)	(858)	2	(868)	(8)
Reserve for Expected Reporting Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	8,206	10,483	8,602	12,235
Plus additions to (reductions in) reserves	2,219	51	3,103	(542)
Less liquidation costs incurred (net of reversals):
Ending Balance	9,178	9,663	9,178	9,663
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred (net of reversals):
Liquidation costs incurred (net of reversals)	(740)	(390)	(1,494)	(975)
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred (net of reversals):
Liquidation costs incurred (net of reversals)	(450)	(450)	(900)	(903)
Reserve for Expected Reporting Costs [Member] | Liquidation Basis of Accounting [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred (net of reversals):
Liquidation costs incurred (net of reversals)	(57)	(31)	(133)	(152)
Reserve for Indenture Trustee/Fiscal and Paying Agent Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	347	446	364	464
Less liquidation costs incurred (net of reversals):
Ending Balance	329	408	329	408
Reserve for Indenture Trustee/Fiscal and Paying Agent Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Governance [Member]
Less liquidation costs incurred (net of reversals):
Liquidation costs incurred (net of reversals)	(18)	(38)	(35)	(56)
Reserve for Residual Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	1,221	1,238	1,223	1,258
Less liquidation costs incurred (net of reversals):
Ending Balance	1,219	1,234	1,219	1,234
Reserve for Residual Wind-Down Costs [Member] | Liquidation Basis of Accounting [Member] | Trust Professionals [Member]
Less liquidation costs incurred (net of reversals):
Liquidation costs incurred (net of reversals)	$ (2)	$ (4)	$ (4)	$ (24)