Quarterly report pursuant to Section 13 or 15(d)

Escrow Deposits (Details)

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Escrow Deposits (Details) (USD $)
In Thousands, unless otherwise specified
1 Months Ended 3 Months Ended 9 Months Ended
Aug. 31, 2013
helicopter
Feb. 28, 2013
helicopter
Sep. 30, 2013
Sep. 30, 2013
Sep. 30, 2012
Jun. 30, 2013
Dec. 31, 2012
Escrow Deposits [Abstract]              
Number of helicopters disposed 2 2          
Proceeds from disposition of property and equipment $ 9,900 $ 18,000 $ 10,200 $ 59,976 $ 4,887    
Escrow deposits     $ 9,900 $ 9,900   $ 16,010 $ 0