Summary of Significant Accounting Policies - Summary of Product Revenue Allowance And Reserve Categories (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)
Trade Discounts, Allowances and Government Chargebacks [Member]
Summary Of Significant Accounting Policies [Line Items]
Provision related to sales in the current year	$ 100
Credit and payments made	(40)
Ending Balance	60
Government Rebates and Other Incentives [Member]
Summary Of Significant Accounting Policies [Line Items]
Provision related to sales in the current year	15
Credit and payments made	0
Ending Balance	15
Returns [Member]
Summary Of Significant Accounting Policies [Line Items]
Provision related to sales in the current year	2
Credit and payments made	0
Ending Balance	2
Product Revenue Allowance and Reserve [Member]
Summary Of Significant Accounting Policies [Line Items]
Provision related to sales in the current year	117
Credit and payments made	(40)
Ending Balance	$ 77

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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