Annual report pursuant to Section 13 and 15(d)

Long-Term Debt (Details)

v3.21.1
Long-Term Debt (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Oct. 30, 2017
USD ($)
Oct. 30, 2017
CAD ($)
Mar. 31, 2021
USD ($)
Mar. 31, 2020
USD ($)
Mar. 31, 2019
USD ($)
Apr. 01, 2018
Debt Instrument [Line Items]              
Less current portion       $ (2,500,000) $ (2,500,000)    
Long-term debt, net of current maturities and deferred debt issuance costs and debt discounts of $2,983 and $4,447 as of March 31, 2021 and 2020, respectively       143,017,000 169,053,000    
Repayments of Long-term Debt       64,963,000 51,883,000 $ 40,323,000  
Debt Instrument, Debt Covenant, Maximum Leverage Ratio to Secure Additional Borrowing   4.0 4.0        
Outstanding borrowings from revolving line of credit              
Debt Instrument [Line Items]              
Line of Credit Facility, Remaining Borrowing Capacity       56,686,000      
Outstanding principal amount of senior secured credit facility              
Debt Instrument [Line Items]              
Long-term debt       $ 145,517,000 $ 171,553,000    
Outstanding borrowings from revolving line of credit | Line of Credit              
Debt Instrument [Line Items]              
Debt instrument, face amount   $ 60,000,000          
Repayments of Lines of Credit   $ 6,000,000          
Consideration transferred, liabilities incurred     $ 201,900        
Debt instrument term   5 years 5 years        
Maximum leverage ratio 3.75            
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          
Variable Rate Term Loan due October 2024              
Debt Instrument [Line Items]              
Debt Instrument, Interest Rate, Effective Percentage       4.75%      
Thermon Heating Systems Inc.              
Debt Instrument [Line Items]              
Debt Proceeds Used as Consideration For Business Acquisition   $ 164,900,000          
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%