Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended								12 Months Ended			36 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Significant Accounting Policies [Line Items]
Impairment losses on short-term investments												$ 0
Allowance for doubtful accounts receivable	$ 3,453,000				$ 0				$ 3,453,000	$ 0		3,453,000
Inventory write-offs									489,000	774,000	$ 0
Impairment of long-lived assets												0
Indirect taxes									1,293,000	972,000	2,275,000
Cost related to charitable care									1,483,000	1,675,000	1,376,000
Shipping and handling costs									5,322,000	3,389,000	1,385,000
Dividends declared									0
Dividends paid									0
Net revenues	53,661,000	$ 50,109,000	$ 38,376,000	$ 34,880,000	30,242,000	$ 21,674,000	$ 17,919,000	$ 13,053,000	177,026,000	82,888,000	33,087,000
Pension expense									1,036,000	529,000	404,000
Severance costs									506,000	430,000	356,000
Increase to trade receivables									23,228,000	6,339,000
Accounting Standards Update 2016-09 [Member]
Significant Accounting Policies [Line Items]
Cumulative deficit effect adjustment resulting from ASU adoption					$ 670,000					670,000
Accounting Standards Update 2014-09 [Member]
Significant Accounting Policies [Line Items]
Cumulative deficit effect adjustment resulting from ASU adoption	$ 2,570,000								2,570,000			$ 2,570,000
Increase to trade receivables									3,215,000
Increase to deferred revenue									645,000
Sales Revenue Net | Customer One | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Net revenues									$ 15,479,000	$ 10,393,000	$ 5,595,000
Concentration risk percentage									9.00%	13.00%	17.00%
Employee Stock Option
Significant Accounting Policies [Line Items]
Share-based award requisite service period									4 years
Expected dividend yield									0.00%	0.00%	0.00%
Field Equipment Under Operating Leases
Significant Accounting Policies [Line Items]
Equipment write-downs included in cost of revenue									$ 195,000	$ 6,436,000	$ 36,000
Field Equipment Under Operating Leases | Minimum
Significant Accounting Policies [Line Items]
Property and equipment useful life									18 months
Field Equipment Under Operating Leases | Maximum
Significant Accounting Policies [Line Items]
Property and equipment useful life									36 months