Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Selected Quarterly Financial Information
Net product sales	$ 16,832	$ 17,540	$ 15,643	$ 14,634	$ 15,393	$ 12,503	$ 11,363	$ 10,729	$ 64,649	$ 49,988	$ 27,132
Net product sales	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Gross profit	$ 9,651	$ 11,093	$ 10,544	$ 8,238	$ 7,631	$ 5,546	$ 4,376	$ 5,508	$ 39,526	$ 23,060	$ 13,102
Net loss attributable to common stock	$ (3,488)	$ (2,051)	$ (3,763)	$ (7,600)	$ (9,337)	$ (12,695)	$ (15,207)	$ (14,436)
Weighted average common shares outstanding used to compute net loss per share, basic and diluted	49,732,654	49,730,755	49,727,718	49,703,563	41,415,358	29,625,792	29,008,909	28,996,956	49,723,772	32,288,555	24,751,091
Net loss per share of common stock, basic and fully diluted	$ (0.07)	$ (0.04)	$ (0.08)	$ (0.15)	$ (0.23)	$ (0.43)	$ (0.52)	$ (0.50)	$ (0.34)	$ (1.60)	$ (2.66)

The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).

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