Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019
Deferred Tax Assets:
Net operating loss	$ 10,823		$ 10,636
Credit carryforwards	1,490		2,895
Deferred compensation	1,681		1,590
Uniform capitalization and inventory	1,067		983
Stock-based compensation	1,079		744
Reserve for accrued employee benefits	929		752
Warranty accrual	655		682
Accrued legal	112		115
Postretirement benefits liability	111		110
Other	379		344
Deferred tax assets	18,326		18,851
Deferred Tax Liabilities:
Depreciation and amortization	(5,035)		(5,138)
Retention and other	(620)		(365)
Deferred tax liabilities	(5,655)		(5,503)
Less: valuation allowance	(9,027)	$ (500)	(8,231)
Net deferred income tax asset	$ 3,644		$ 5,117