Quarterly report pursuant to Section 13 or 15(d)

Balance Sheet Components - Summary of Property Plant and Equipment and Rental Equipment with Associated Accumulated Depreciation (Details)

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Balance Sheet Components - Summary of Property Plant and Equipment and Rental Equipment with Associated Accumulated Depreciation (Details) - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 31, 2017
Property Plant And Equipment [Line Items]    
Property and equipment $ 66,315 $ 64,568
Accumulated depreciation 44,343 44,465
Property and equipment, net 21,972 20,103
Equipment    
Property Plant And Equipment [Line Items]    
Property and equipment 46,638 49,349
Accumulated depreciation 33,822 34,754
Property and equipment, net 12,816 14,595
Other property and equipment    
Property Plant And Equipment [Line Items]    
Property and equipment 19,677 15,219
Accumulated depreciation 10,521 9,711
Property and equipment, net $ 9,156 $ 5,508