Reserves for Expected Costs of Liquidation and Residual Wind-Down Claims and Costs - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Restructuring Cost and Reserve [Line Items]
Net increase (decrease in) additions to reserves for Expected Costs of Liquidation	$ 1,522	$ 9,511	$ 33,948
Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Expected liquidation end date	Jul. 31, 2021
Reserve for Expected Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Net increase (decrease in) additions to reserves for Expected Costs of Liquidation	$ 5,059	4,122	25,351
Reserve for Expected Reporting Costs [Member]
Restructuring Cost and Reserve [Line Items]
Net increase (decrease in) additions to reserves for Expected Costs of Liquidation	$ (3,537)	$ 5,389	$ 8,597