Income Taxes - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018	Mar. 31, 2017
Tax Credit Carryforward [Line Items]
Current tax benefit or provision		$ 0	$ 0	$ 0	$ 0
Income taxes paid		0	0	0	0
Deferred tax benefit or provision		$ 0	$ 0	0	$ 0
Federal income tax rate	37.00%	37.00%	39.60%
Capital losses carryovers		$ 1,700,000		1,700,000
Net operating loss carryovers		139,700,000		$ 139,700,000
Remaining capital loss carryovers expire				Mar. 31, 2020
Net operating loss carryovers begin to expire				Mar. 31, 2032
Deferred tax asset		52,301,000		$ 52,301,000
Deferred tax assets, valuation allowance		59,456,000		59,456,000
Change in valuation allowance against net deferred tax assets		$ 100,000		$ (700,000)
Tax Year 2013 [Member]
Tax Credit Carryforward [Line Items]
Capital losses carryovers						$ 22,600,000
Tax Year 2012 [Member]
Tax Credit Carryforward [Line Items]
Capital losses carryovers							$ 158,100,000
Internal Revenue Service (IRS) [Member]
Tax Credit Carryforward [Line Items]
Statutory notification period				60 days