Annual report pursuant to Section 13 and 15(d)

ESCROW DEPOSITS Escrow Deposits (Details)

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ESCROW DEPOSITS Escrow Deposits (Details)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
USD ($)
helicopter
Dec. 31, 2016
USD ($)
helicopter
Dec. 31, 2015
USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Deposits in like-kind exchange escrow accounts $ 3,300 $ 3,800  
Proceeds from disposition of property and equipment 9,392 28,609 $ 25,328
Purchases of property and equipment $ 16,770 $ 39,200 $ 60,050
AW169 Light Twin Helicopters      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of disposals | helicopter   1  
Proceeds from disposition of property and equipment   $ 3,200  
AW139 Helicopter      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of disposals | helicopter 2    
Proceeds from disposition of property and equipment $ 18,200    
AW189 Heavy Helicopters      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Purchases of property and equipment 7,400    
S92 Heavy Helicopters      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Purchases of property and equipment $ 7,000