Summary of Significant Accounting Policies - Summary of Product Revenue Allowance And Reserve Categories (Detail) $ in Thousands	6 Months Ended
Jun. 30, 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	486
Credit and payments made	(308)
Ending Balance	238
Government Rebates and Other Incentives [Member]
Summary Of Significant Accounting Policies [Line Items]
Beginning Balance	15
Provision related to sales in the current year	133
Ending Balance	148
Returns [Member]
Summary Of Significant Accounting Policies [Line Items]
Beginning Balance	2
Provision related to sales in the current year	34
Ending Balance	36
Product Revenue Allowance and Reserve [Member]
Summary Of Significant Accounting Policies [Line Items]
Beginning Balance	77
Provision related to sales in the current year	653
Credit and payments made	(308)
Ending Balance	$ 422

Summary of significant accounting policies.

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- Definition

Amount of valuation and qualifying accounts and reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-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

+ Details

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Amount of increase in valuation and qualifying accounts and reserves from charge to cost and expense.

+ References

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Amount of decrease in valuation and qualifying accounts and reserves.

+ References

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