Reserves for Expected Costs of Liquidation and Residual Wind-Down Claims and Costs - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2019
Restructuring Cost and Reserve [Line Items]
Net increase (decrease in) additions to reserves for Expected Costs of Liquidation	$ 31,517		$ 13,053	$ 27,504	$ 8,579
Expected liquidation end date		Jan. 31, 2022		Oct. 31, 2023
Reserves For Residual Wind Down Claims And Costs	169			$ 169		$ 169
Legal Fees Reimbursement [Member]
Restructuring Cost and Reserve [Line Items]
Loss contingency Inestimable loss	10,000			10,000
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	23,578		6,824	20,723	4,423
Reserves For Residual Wind Down Claims And Costs	200			200
Reserve for Expected Reporting Costs [Member]
Restructuring Cost and Reserve [Line Items]
Net increase (decrease in) additions to reserves for Expected Costs of Liquidation	$ 7,939		$ 6,229	$ 6,781	$ 4,156