Annual report pursuant to Section 13 and 15(d)

SUPPLEMENTAL INFORMATION FOR STATEMENTS OF CASH FLOWS Schedule of Supplemental Cash Flow Disclosures (Details)

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SUPPLEMENTAL INFORMATION FOR STATEMENTS OF CASH FLOWS Schedule of Supplemental Cash Flow Disclosures (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]      
Income taxes paid, net of refunds   $ (5,978) $ 5,960
Interest paid to others, excluding capitalized interest   15,268 12,642
Schedule of non-cash investing and financing activities:      
Contribution of notes payable as additional capital into Aeróleo $ 0   0
Settlement of accrued contingent liabilities through installment obligations 386   0
Company financed sale of equipment and parts $ 0 $ 0 $ 1,248