Number of financial institutions.

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- Definition

Amount of asset related to consideration paid in advance for research and development expenses that provide economic benefits within a future period of one year or the normal operating cycle, if longer.

+ References

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- Definition

Summary Of Significant Accounting Policies [Line Items]

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- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) Financial_Institution Segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016	Jan. 01, 2019 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Prepaid R&D expense	$ 4,377	$ 1,287
Expected dividend yield	0.00%	0.00%	0.00%
Number of operating segments \| Segment	1
Maximum [Member] \| ASU 2016-02 [Member] \| Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating lease, liability				$ 6,000
Minimum [Member] \| ASU 2016-02 [Member] \| Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating lease, liability				$ 5,000
Employee Options [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected life of options (in years)	6 years 3 months
Nonemployee Options [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected life of options (in years)		10 years	10 years
Nonemployee Options [Member] \| Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected life of options (in years)	10 years
Cash And Cash Equivalents And Marketable Securities [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of financial institutions \| Financial_Institution	3