Annual report pursuant to Section 13 and 15(d)

LONG-TERM DEBT - Narrative (Details)

v3.8.0.1
LONG-TERM DEBT - Narrative (Details) - USD ($)
 12 Months Ended
Dec. 20, 2015
Dec. 01, 2015
Dec. 07, 2012
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Mar. 07, 2018
Mar. 06, 2018
Mar. 31, 2014
Dec. 23, 2010
Nov. 24, 2010
Debt Instrument [Line Items]                      
Outstanding borrowings       $ 208,446,000 $ 236,376,000            
Gain on debt extinguishment       0 518,000 $ 1,617,000          
Write off of debt issuance cost       500,000              
Long-term debt issuance costs       $ 0 $ (886,000) $ (71,000)          
7.750% Senior Notes (excluding unamortized discount) | Senior Unsecured Notes Due December 15, 2022                      
Debt Instrument [Line Items]                      
Face amount     $ 200,000,000.0                
Stated interest rate     7.75% 7.75% 7.75%            
Proceeds from issuance of long-term debt     $ 191,900,000                
Outstanding borrowings     200,000,000.0                
Debt obligations       $ 5,000,000              
Redemption price (in dollars per share)       86.63              
Repayments of debt       4,500,000              
Accrued interest paid       200,000              
Gain on debt extinguishment         $ 518,000.00            
Promissory notes                      
Debt Instrument [Line Items]                      
Outstanding borrowings       $ 21,642,000 $ 23,166,000            
Promissory notes | Promissory Note to Purchase Heavy Helicopter                      
Debt Instrument [Line Items]                      
Face amount                   $ 27,000,000.0  
Outstanding borrowings $ 19,000,000                    
Debt instrument, interest rate at year-end       2.47%              
Note required monthly payments 100,000                    
Note required final payment $ 12,800,000                    
Promissory notes | Promissory Note to Purchase Medium Helicopter                      
Debt Instrument [Line Items]                      
Face amount                     $ 11,700,000.0
Outstanding borrowings   $ 5,900,000                  
Debt instrument, interest rate at year-end       2.43%              
Note required monthly payments   100,000.0                  
Note required final payment   $ 4,000,000                  
Senior secured revolving credit facility                      
Debt Instrument [Line Items]                      
Line of credit facility, maximum borrowing capacity       $ 200,000,000.0         $ 200,000,000.0    
Maximum commitment increase amount                 100,000,000.0    
Remaining borrowing capacity       75,800,000              
Letters of credit outstanding       1,300,000              
Senior secured revolving credit facility | Promissory notes                      
Debt Instrument [Line Items]                      
Repayments of borrowings outstanding     $ 190,000,000                
Letter of Credit                      
Debt Instrument [Line Items]                      
Line of credit facility, maximum borrowing capacity                 $ 50,000,000.0    
Brazil | Other litigation matters                      
Debt Instrument [Line Items]                      
Installment payments       $ 3,000,000              
Subsequent Event | Senior secured revolving credit facility                      
Debt Instrument [Line Items]                      
Line of credit facility, maximum borrowing capacity             $ 125,000,000.0 $ 200,000,000.0      
Interest coverage ratio             175.00%        
Senior secured leverage ratio             325.00%