Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Summary of Depreciation and Amortization Expense of Property and Equipment and Rental Equipment (Details)

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Summary of Significant Accounting Policies - Summary of Depreciation and Amortization Expense of Property and Equipment and Rental Equipment (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Property Plant And Equipment [Line Items]      
Depreciation $ 11,429 $ 11,965 $ 10,339
Depreciation and amortization 13,457 13,926 11,930
Equipment      
Property Plant And Equipment [Line Items]      
Depreciation 11,429 11,965 10,339
Other property and equipment      
Property Plant And Equipment [Line Items]      
Depreciation and amortization $ 2,028 $ 1,961 $ 1,591