Annual report pursuant to Section 13 and 15(d)

VARIABLE INTEREST ENTITIES AND EQUITY INVESTMENTS AND ADVANCES Era Training Center Narrative (Details)

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VARIABLE INTEREST ENTITIES AND EQUITY INVESTMENTS AND ADVANCES Era Training Center Narrative (Details)
$ in Thousands
 12 Months Ended
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
simulator
Dec. 31, 2017
USD ($)
Schedule of Equity Method Investments [Line Items]      
Proceeds from sale $ 34,712 $ 1,000  
Equity Method Investee | Training Services      
Schedule of Equity Method Investments [Line Items]      
Notes Receivable, Principal, Related Parties   3,600  
Notes receivable to related party   $ 3,700  
Number of flight simulators sold | simulator   3  
Proceeds from sale   $ 2,900  
Equity Method Investee | Additional Simulator      
Schedule of Equity Method Investments [Line Items]      
Notes receivable to related party   400  
Payments for purchase of other assets   400  
Era Training Center | Equity Method Investee | Helicopter, Management and Other Services      
Schedule of Equity Method Investments [Line Items]      
Expenses from transactions with related party   100 $ 200
Era Training Center | Equity Method Investee | Training Services      
Schedule of Equity Method Investments [Line Items]      
Expenses from transactions with related party   $ 200 $ 500