Annual report pursuant to Section 13 and 15(d)

Revenue Recognition - Additional Information (Detail)

v3.21.1
Revenue Recognition - Additional Information (Detail) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2021
Dec. 31, 2020
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2021
Mar. 31, 2020
Mar. 31, 2019
Contract With Customer Assets And Liabilities [Line Items]                      
Net sales $ 25,671,000 $ 27,154,000 $ 27,954,000 $ 16,710,000 $ 23,082,000 $ 25,286,000 $ 21,643,000 $ 20,593,000 $ 97,489,000 $ 90,604,000 $ 91,831,000
Percentage of revenue from contracts recognized over time                 60.00% 70.00% 60.00%
Percentage of revenue from contracts recognized upon shipment                 40.00% 30.00% 40.00%
Revenue recognized included in contract liability                 $ 20,833,000    
Unbilled revenue (contract assets)                 5,402,000    
Contract with customer liability increase in contract asset due to contract progress.                 29,836,000    
Contract with customer liability offset by invoicing to customers.                 24,434,000    
Customer deposits, current                 12,924,000    
Contract with customer liability offset by new customer deposits                 7,909,000    
Receivables billed but not paid under retainage provisions in its customer contracts 3,747,000       2,016,000       3,747,000 $ 2,016,000  
Revenue remaining unsatisfied performance obligations amount 137,567,000               137,567,000    
Customer Deposit [Member]                      
Contract With Customer Assets And Liabilities [Line Items]                      
Contract liabilities 1,603,000       3,660,000       1,603,000 3,660,000  
Prepaid Expenses and Other Current Assets [Member]                      
Contract With Customer Assets And Liabilities [Line Items]                      
Capitalized costs, net of amortization $ 39,000       $ 45,000       39,000 45,000  
Amortization expense                 600,000 169,000 $ 168,000
Sudan [Member]                      
Contract With Customer Assets And Liabilities [Line Items]                      
Net sales                 0 0 0
Iran [Member]                      
Contract With Customer Assets And Liabilities [Line Items]                      
Net sales                 0 0 0
Syria [Member]                      
Contract With Customer Assets And Liabilities [Line Items]                      
Net sales                 $ 0 $ 0 $ 0