Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Details)

v3.8.0.1
Summary of Significant Accounting Policies - Additional Information (Details)
 3 Months Ended 12 Months Ended
Dec. 31, 2017
USD ($)
Dec. 31, 2018
Dec. 31, 2017
USD ($)
Product
Customer
Segment
Dec. 31, 2016
USD ($)
Customer
Dec. 31, 2015
USD ($)
Customer
Dec. 31, 2014
USD ($)
Significant Accounting Policies [Line Items]            
Accrual of product warranty liability $ 6,171,000   $ 6,171,000 $ 3,480,000 $ 1,973,000 $ 1,115,000
Extended service contracts     The second deliverable is the lifetime warranty that provides for a functional oxygen concentrator for the remaining lifetime of the patient      
Number of deliverables when a product that includes lifetime warranty is sold | Product     2      
Standard product warranty description     The first deliverable is the oxygen concentrator equipment which comes with a standard warranty of three years and the additional service component is broken out from the product sales and deferred and recognized in years four and five to correspond with the service period.      
Standard warranty period offered     3 years      
Estimation for sale of products     the Company estimates that 60% of its patients will succumb to their disease within three years of initial diagnosis. Given the approximate mortality rate of 20% per year, the Company estimates on average its patients will succumb to their disease within five years of initial diagnosis.      
Deferred capped rental revenue 0   $ 0 0    
Rental revenue earned     30-day period      
Accounts receivable, net 31,444,000   $ 31,444,000 30,828,000    
Unbilled Receivables 1,470,000   1,470,000 7,484,000    
Increase in provision for bad debt and revenue adjustments related to prior years     $ 3,442,000 3,589,000    
Percentage of Non-US revenue invoiced in Euros     73.50%      
Transfer of inventory to rental equipment     $ 1,055,000 1,454,000 1,449,000  
Salvage value of expenditures for additions, improvements and replacements 0   0      
Repairs and maintenance expense     2,385,000 2,464,000 2,520,000  
Depreciation and amortization     11,795,000 13,457,000 13,926,000  
Impairments of long-lived assets     0 0    
Advertising costs     12,511,000 6,215,000 4,686,000  
Unrecognized tax benefits, interest or penalties recognized     $ 0 $ 0 $ 0  
Corporate tax rate     34.00% 34.00% 34.00%  
Provision for income taxes related TCJA 7,578,000          
Number of operating segments | Segment     1      
Number of reportable segments | Segment     1      
Scenario, Forecast            
Significant Accounting Policies [Line Items]            
Corporate tax rate   21.00%        
Construction in Process and Computer Software or Development Cost            
Significant Accounting Policies [Line Items]            
Depreciation and amortization     $ 0 $ 0    
Other Noncurrent Assets            
Significant Accounting Policies [Line Items]            
Noncurrent inventories expected to be realized or consumed 644,000   644,000 314,000    
Medicare            
Significant Accounting Policies [Line Items]            
Accounts receivable, net 1,501,000   1,501,000 7,208,000    
Customer Concentration Risk | Customer One            
Significant Accounting Policies [Line Items]            
Accounts receivable, net 10,394,000   10,394,000 $ 9,791,000    
Customer Concentration Risk | Customer Two            
Significant Accounting Policies [Line Items]            
Accounts receivable, net 6,459,000   $ 6,459,000      
Sales Revenue, Net | Customer Concentration Risk            
Significant Accounting Policies [Line Items]            
Number of customers | Customer     1 1 0  
Concentration risk, percentage     7.00% 12.40% 21.00%  
Net Accounts Receivable | Customer Concentration Risk            
Significant Accounting Policies [Line Items]            
Number of customers | Customer     2 1    
Concentration risk, percentage     4.70% 23.40%    
Sales Revenue, Services, Net | Customer Concentration Risk            
Significant Accounting Policies [Line Items]            
Concentration risk, percentage     73.00% 72.60% 73.70%  
Raw materials | Supplier Concentration Risk | Vendor one            
Significant Accounting Policies [Line Items]            
Concentration risk, percentage     19.70% 21.00%    
Raw materials | Supplier Concentration Risk | Vendor two            
Significant Accounting Policies [Line Items]            
Concentration risk, percentage     15.40% 15.60%    
Raw materials | Supplier Concentration Risk | Vendor three            
Significant Accounting Policies [Line Items]            
Concentration risk, percentage     9.50% 8.60%    
Forward Contracts            
Significant Accounting Policies [Line Items]            
Payable $ 66,000   $ 66,000      
Accounts receivable, net       $ 15,000