Annual report pursuant to Section 13 and 15(d)

Acquisitions - Schedule of Assets Acquired and Liabilities Assumed WTL Oil (Details)

v3.19.1
Acquisitions - Schedule of Assets Acquired and Liabilities Assumed WTL Oil (Details) - USD ($)
$ in Thousands
 12 Months Ended
May 31, 2018
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Business Acquisition [Line Items]        
Goodwill   $ 101,245 $ 99,811 $ 88,727
WTL Oil LLC        
Business Acquisition [Line Items]        
Property, plant and equipment $ 2,960      
Goodwill 1,567      
Total assets acquired $ 6,107      
Minimum | WTL Oil LLC        
Business Acquisition [Line Items]        
Acquired finite-lived intangible assets, weighted average useful life (in years) 10 years      
Maximum | WTL Oil LLC        
Business Acquisition [Line Items]        
Acquired finite-lived intangible assets, weighted average useful life (in years) 20 years      
Customer relationships        
Business Acquisition [Line Items]        
Acquired finite-lived intangible assets, weighted average useful life (in years)   6 years 10 months 15 days    
Customer relationships | WTL Oil LLC        
Business Acquisition [Line Items]        
Identifiable intangible assets $ 930      
Trade names        
Business Acquisition [Line Items]        
Acquired finite-lived intangible assets, weighted average useful life (in years)   8 years 11 months 20 days    
Trade names | WTL Oil LLC        
Business Acquisition [Line Items]        
Identifiable intangible assets $ 650