Annual report pursuant to Section 13 and 15(d)

NATURE OF OPERATIONS AND ACCOUNTING POLICIES Revenue Recognition Narrative (Details)

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NATURE OF OPERATIONS AND ACCOUNTING POLICIES Revenue Recognition Narrative (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2015
Oct. 01, 2015
Sep. 30, 2015
Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]          
Deferred revenue   $ 0     $ 31,047
Minimum          
Schedule of Equity Method Investments [Line Items]          
Service agreement period 1 month        
Service agreement cancellation period 30 days        
Hospital service agreement termination period 1 year        
Maximum          
Schedule of Equity Method Investments [Line Items]          
Service agreement period 5 years        
Service agreement cancellation period 90 days        
Hospital service agreement termination period 5 years        
Aeroleo | Variable Interest Entity, Not Primary Beneficiary          
Schedule of Equity Method Investments [Line Items]          
Percent of economic interest     50.00%    
Percent of voting interest     80.00%    
Equity Method Investee | Aeroleo | Aeroleo          
Schedule of Equity Method Investments [Line Items]          
Deferred revenue       $ 42,100