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, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Beginning Balance	$ 6,650	$ 59,759	$ 28,712	$ 37,485
Less reductions in reserves	(1,670)		(8,005)
Plus net additions to reserves		1,634		29,138
Less liquidation costs incurred:
Ending Balance	2,751	59,065	2,751	59,065
Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(976)	(1,120)	(3,141)	(4,068)
Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(1,010)	(1,080)	(3,068)	(3,229)
Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(243)	(128)	(11,747)	(261)
Reserve for Expected Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	4,312	41,065	22,530	23,379
Less reductions in reserves	(1,501)		(6,167)
Plus net additions to reserves		1,639		22,362
Less liquidation costs incurred:
Ending Balance	1,649	41,488	1,649	41,488
Reserve for Expected Wind-Down Costs [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(453)	(567)	(1,429)	(2,309)
Reserve for Expected Wind-Down Costs [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(551)	(615)	(1,709)	(1,852)
Reserve for Expected Wind-Down Costs [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(158)	(34)	(11,576)	(92)
Reserve for Expected Reporting Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	2,256	18,596	6,100	13,996
Less reductions in reserves	(169)	(5)	(1,838)
Plus net additions to reserves				6,776
Less liquidation costs incurred:
Ending Balance	1,029	17,494	1,029	17,494
Reserve for Expected Reporting Costs [Member] | Trust Professionals [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(523)	(553)	(1,712)	(1,759)
Reserve for Expected Reporting Costs [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(450)	(450)	(1,350)	(1,350)
Reserve for Expected Reporting Costs [Member] | Other Administrative Expenses [Member]
Less liquidation costs incurred:
Liquidation costs incurred	(85)	(94)	(171)	(169)
Reserve for Indenture Trustee/Fiscal and Paying Agent Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	82	98	82	110
Less liquidation costs incurred:
Ending Balance	73	83	73	83
Reserve for Indenture Trustee/Fiscal and Paying Agent Costs [Member] | Trust Governance [Member]
Less liquidation costs incurred:
Liquidation costs incurred	$ (9)	$ (15)	$ (9)	$ (27)