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Supplemental Balance Sheet Information - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Supplemental Balance Sheet Information [Line Items]          
Property and equipment, gross $ 22,329   $ 22,329   $ 20,655
T2 Owned Instruments in Service [Member]          
Supplemental Balance Sheet Information [Line Items]          
Property and equipment, gross 7,900   $ 7,900   $ 5,700
Estimated useful lives (in years)     5 years    
Depreciation expense recorded as a component of cost of product revenue $ 200 $ 200 $ 700 $ 400