Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurement - Fair Value of Assets and Liabilities Measured on a Recurring Basis (Details)

v3.19.1
Fair Value Measurement - Fair Value of Assets and Liabilities Measured on a Recurring Basis (Details) - Recurring - USD ($)
$ in Thousands
Mar. 31, 2019
Dec. 31, 2018
Liabilities:    
Total liabilities $ 6,149 $ 6,027
Level 2    
Assets:    
Total assets 318 766
Level 2 | Interest rate swap instruments    
Assets:    
Total assets 285 733
Liabilities:    
Liability derivatives 3,990 3,187
Level 2 | Commodity swap instruments    
Assets:    
Total assets 33 33
Liabilities:    
Liability derivatives 70 70
Level 2 | Interest make-whole provisions    
Liabilities:    
Liability derivatives 1,085 1,808
Level 3    
Liabilities:    
Contingent revenue earn-out $ 1,004 $ 962