Annual report pursuant to Section 13 and 15(d)

Long-Term Debt (Details)

v3.20.1
Long-Term Debt (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Oct. 30, 2017
CAD ($)
Oct. 30, 2017
USD ($)
Mar. 31, 2020
USD ($)
Mar. 31, 2019
USD ($)
Mar. 31, 2018
USD ($)
Apr. 01, 2018
Debt Instrument [Line Items]              
Less current portion       $ (2,500,000) $ (2,500,000)    
Debt issuance costs, net       4,447,000 6,271,000    
Repayments of Long-term Debt       51,883,000 40,323,000 $ 116,000,000  
Debt Instrument, Debt Covenant, Maximum Leverage Ratio to Secure Additional Borrowing   4.0 4.0        
Line of Credit Facility, Remaining Borrowing Capacity       56,012      
Borrowings under revolving credit facility       0 11,225,000    
Outstanding principal amount of senior secured credit facility              
Debt Instrument [Line Items]              
Long-term debt       $ 171,553,000 $ 200,229,000    
Outstanding borrowings from revolving line of credit | Line of Credit              
Debt Instrument [Line Items]              
Debt instrument, face amount     $ 60,000,000        
Debt instrument term   5 years 5 years        
Repayments of Lines of Credit     $ 6,000,000        
Consideration transferred, liabilities incurred   $ 201,900          
Debt Instrument, Debt Covenant, Coverage Ratio   1.25 1.25        
Variable Rate Senior Secured Term Loan B | Secured Debt              
Debt Instrument [Line Items]              
Debt instrument, face amount     $ 250,000,000        
Debt instrument term   7 years 7 years        
Debt Instrument, Quarterly Amortization, Percent             0.25%
Debt Instrument, Prepayment Premium   1.00% 1.00%        
Debt Instrument, Debt Covenant, Repayment requirement, Percentage of Excess Cash Flow       50.00%      
Debt Instrument, Debt Covenant, Reduced Repayment Requirement, Percentage of Excess Cash Flow       25.00%      
Debt Instrument, Debt Covenant, Maximum Leverage Ratio Requirement For Reduced Repayment       4.0      
Debt Instrument, Debt Covenant, Minimum Leverage Ratio Requirement For Reduced Repayment       3.5      
Debt Instrument, Debt Covenant, Minimum Repayment Requirement, Percentage of Excess Cash Flow       0.00%      
Debt Instrument, Debt Covenant, Maximum Leverage Ratio Requirement For Minimum Repayment       3.5      
Line of Credit Facility, Additional Borrowing Capacity     $ 30,000,000        
Term Loan A due April 2019              
Debt Instrument [Line Items]              
Repayments of Long-term Debt     70,875,000        
Thermon Heating Systems Inc.              
Debt Instrument [Line Items]              
Debt Proceeds Used as Consideration For Business Acquisition     $ 164,900,000        
Scenario, Forecast | Outstanding borrowings from revolving line of credit | Line of Credit              
Debt Instrument [Line Items]              
Maximum leverage ratio 3.75            
Subsidiary Equity | Variable Rate Senior Secured Term Loan B | Secured Debt              
Debt Instrument [Line Items]              
Guarantor Obligations, Liquidation Proceeds, Percentage   100.00% 100.00%        
Stock of First Tier Material Foreign Subsidiaries, Domestic Borrower, and Domestic Subsidiary | Variable Rate Senior Secured Term Loan B | Secured Debt              
Debt Instrument [Line Items]              
Guarantor Obligations, Liquidation Proceeds, Percentage   65.00% 65.00%        
Base Rate | Outstanding borrowings from revolving line of credit | Line of Credit              
Debt Instrument [Line Items]              
Debt Instrument, Basis Spread on Variable Rate   2.25% 2.25%        
Base Rate | Variable Rate Senior Secured Term Loan B | Secured Debt              
Debt Instrument [Line Items]              
Debt Instrument, Basis Spread on Variable Rate   2.75% 2.75%        
London Interbank Offered Rate (LIBOR) | Outstanding borrowings from revolving line of credit | Line of Credit              
Debt Instrument [Line Items]              
Debt Instrument, Basis Spread on Variable Rate   3.25% 3.25%        
London Interbank Offered Rate (LIBOR) | Variable Rate Senior Secured Term Loan B | Secured Debt              
Debt Instrument [Line Items]              
Debt Instrument, Basis Spread on Variable Rate   3.75% 3.75%        
Canadian Base Rate | Outstanding borrowings from revolving line of credit | Line of Credit              
Debt Instrument [Line Items]              
Debt Instrument, Basis Spread on Variable Rate   2.25% 2.25%        
CDOR | Outstanding borrowings from revolving line of credit | Line of Credit              
Debt Instrument [Line Items]              
Debt Instrument, Basis Spread on Variable Rate   3.25% 3.25%