Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Computation of Depreciation and Amortization Using Straight Line Method Over Estimated Useful Lives of Assets (Details)

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Summary of Significant Accounting Policies - Computation of Depreciation and Amortization Using Straight Line Method Over Estimated Useful Lives of Assets (Details)
12 Months Ended
Dec. 31, 2017
Rental equipment | Minimum  
Property Plant And Equipment [Line Items]  
Property Plant And Equipment Useful Life 1 year 6 months
Rental equipment | Maximum  
Property Plant And Equipment [Line Items]  
Property Plant And Equipment Useful Life 5 years
Manufacturing equipment and tooling | Minimum  
Property Plant And Equipment [Line Items]  
Property Plant And Equipment Useful Life 2 years
Manufacturing equipment and tooling | Maximum  
Property Plant And Equipment [Line Items]  
Property Plant And Equipment Useful Life 5 years
Computer equipment and software | Minimum  
Property Plant And Equipment [Line Items]  
Property Plant And Equipment Useful Life 2 years
Computer equipment and software | Maximum  
Property Plant And Equipment [Line Items]  
Property Plant And Equipment Useful Life 3 years
Furniture and equipment | Minimum  
Property Plant And Equipment [Line Items]  
Property Plant And Equipment Useful Life 3 years
Furniture and equipment | Maximum  
Property Plant And Equipment [Line Items]  
Property Plant And Equipment Useful Life 5 years
Leasehold improvements  
Property Plant And Equipment [Line Items]  
Property Plant And Equipment Useful Life Lesser of estimated useful life or remaining lease term