Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2013	Mar. 31, 2012
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
Capital losses carryovers	1,700,000		1,700,000		$ 1,700,000	$ 1,700,000	$ 22,600,000	$ 158,100,000
Net operating loss carryovers	139,100,000		$ 139,100,000
Remaining capital loss carryovers expire			Mar. 31, 2020
Net operating loss carryovers begin to expire			Mar. 31, 2032
Deferred tax asset	52,085,000		$ 52,085,000
Deferred tax assets, valuation allowance	64,389,000		64,389,000
Change in valuation allowance against net deferred tax assets	$ 5,300,000		$ 9,600,000
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