Summary of Significant Accounting Policies - Summary of Product Revenue Allowance And Reserve Categories (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2018 USD ($)
Trade Discounts, Allowances and Government Chargebacks [Member]
Summary Of Significant Accounting Policies [Line Items]
Beginning Balance	$ 60
Provision related to sales in the current year	186
Credit and payments made	(94)
Ending Balance	152
Government Rebates and Other Incentives [Member]
Summary Of Significant Accounting Policies [Line Items]
Beginning Balance	15
Provision related to sales in the current year	49
Ending Balance	64
Returns [Member]
Summary Of Significant Accounting Policies [Line Items]
Beginning Balance	2
Provision related to sales in the current year	12
Ending Balance	14
Product Revenue Allowance and Reserve [Member]
Summary Of Significant Accounting Policies [Line Items]
Beginning Balance	77
Provision related to sales in the current year	247
Credit and payments made	(94)
Ending Balance	$ 230

Summary of significant accounting policies.

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- Definition

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

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- Definition

Amount of increase in the allowances and reserves, which consist of the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs, from charges to costs and expenses.

+ References

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- Definition

Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively.

+ References

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