Annual report pursuant to Section 13 and 15(d)

Restructuring and other charges (income) - Narrative (Details)

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Restructuring and other charges (income) - Narrative (Details)
3 Months Ended 12 Months Ended
Dec. 15, 2020
USD ($)
Dec. 15, 2020
ZAR (R)
Mar. 31, 2021
USD ($)
Mar. 31, 2021
USD ($)
positions
Mar. 31, 2020
USD ($)
Mar. 31, 2019
USD ($)
Restructuring Cost and Reserve [Line Items]            
Number of positions eliminated | positions       252,000    
Severance costs       $ 5,748,000    
Lease abandonment charges       381,000    
Sale of stock, consideration received on transaction $ 167,000 R 2,500,000        
Loss on disposition of business       (2,065,000) $ 0 $ 0
Accumulated other comprehensive loss     $ (35,919,000) $ (35,919,000) $ (63,894,000)  
Thermon South Africa Proprieary Limited            
Restructuring Cost and Reserve [Line Items]            
Sale of stock, percentage of ownership before transaction 100.00% 100.00%        
Loss on disposition of business $ 2,065,000          
Accumulated other comprehensive loss $ 828,000          
Canada            
Restructuring Cost and Reserve [Line Items]            
Lease abandonment charges     $ 429,000