Annual report pursuant to Section 13 and 15(d)

VARIABLE INTEREST ENTITIES AND EQUITY INVESTMENTS AND ADVANCES Schedule of Equity Method Investments (Details)

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VARIABLE INTEREST ENTITIES AND EQUITY INVESTMENTS AND ADVANCES Schedule of Equity Method Investments (Details) - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]    
Equity method investments $ 27,112 $ 30,056
Cumulative unfunded net losses of equity investees $ 6,000 2,900
Dart Helicopter Services LLC    
Schedule of Equity Method Investments [Line Items]    
Ownership 50.00%  
Equity method investments $ 27,112 26,128
Era Training Center    
Schedule of Equity Method Investments [Line Items]    
Ownership 50.00%  
Equity method investments $ 0 $ 3,928