Reserves for Expected Costs of Liquidation and Residual Wind-Down Claims and Costs - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Restructuring Cost and Reserve [Line Items]
Net increase additions to reserves for Expected Costs of Liquidation	$ 33,948	$ 12,123	$ 7,711
Expected liquidation end date	Nov. 30, 2020
Reserve for Expected Wind-Down Costs [Member]
Restructuring Cost and Reserve [Line Items]
Net increase additions to reserves for Expected Costs of Liquidation	$ 25,351	5,325	5,592
Reserve for Expected Reporting Costs [Member]
Restructuring Cost and Reserve [Line Items]
Net increase additions to reserves for Expected Costs of Liquidation	$ 8,597	$ 6,798	$ 2,119