Annual report pursuant to Section 13 and 15(d)

VARIABLE INTEREST ENTITIES AND EQUITY INVESTMENTS AND ADVANCES Schedule of Equity Method Investment, Financial Information, Balance Sheets (Details)

v3.8.0.1
VARIABLE INTEREST ENTITIES AND EQUITY INVESTMENTS AND ADVANCES Schedule of Equity Method Investment, Financial Information, Balance Sheets (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Dart Helicopter Services LLC    
Schedule of Equity Method Investments [Line Items]    
Current assets $ 29,336 $ 28,442
Non-current assets 29,899 29,475
Current liabilities 6,671 6,737
Non-current liabilities 6,096 8,315
Other Investments    
Schedule of Equity Method Investments [Line Items]    
Current assets 257 535
Non-current assets 4,138 4,641
Current liabilities 654 653
Non-current liabilities $ 3,298 $ 3,652