Quarterly report pursuant to Section 13 or 15(d)

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

v3.10.0.1
Fair Value Measurement- Fair Value of Liabilities Measured on a Recurring Basis (Details) - Recurring - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 31, 2017
Assets:    
Total assets $ 1,319 $ 233
Liabilities:    
Total liabilities 2,480 3,529
Level 2 | Interest rate swap instruments    
Assets:    
Total assets 1,298 233
Liabilities:    
Total liabilities 2,414 3,529
Level 2 | Commodity swap instruments    
Assets:    
Total assets 21 0
Liabilities:    
Total liabilities $ 66 $ 0