Quarterly report pursuant to Section 13 or 15(d)

Acquisitions - Narrative (Details)

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Acquisitions - Narrative (Details)
CAD in Thousands, $ in Thousands
3 Months Ended 9 Months Ended
Oct. 30, 2017
CAD
Oct. 30, 2017
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Mar. 31, 2017
USD ($)
Business Acquisition [Line Items]              
Weighted average useful life     10 years 7 months 6 days        
Goodwill     $ 216,198   $ 216,198   $ 122,521
Revenues     92,660 $ 64,340 206,027 $ 196,548  
Thermon Heating Systems Inc.              
Business Acquisition [Line Items]              
Equity interests acquired 100.00% 100.00%          
Payments to acquire business CAD 261,950 $ 204,235          
Transaction costs     3,839   3,839    
Revenues     16,057   2,851    
Operating Segments              
Business Acquisition [Line Items]              
Goodwill acquired         87,540    
Goodwill     216,198   216,198   122,521
Revenues     92,660 $ 64,340 206,027 $ 196,548  
Operating Segments | Canada              
Business Acquisition [Line Items]              
Goodwill     $ 134,987   134,987   $ 43,444
Operating Segments | Canada | Thermon Heating Systems Inc.              
Business Acquisition [Line Items]              
Goodwill acquired         $ 87,540