Commitments and Contingencies - Additional Information (Detail) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($) ft² Lease	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Number of operating leases \| Lease	3
General office, laboratory, and research and development space leased \| ft²	107,901
Deferred rent liability	$ 8.2	$ 8.7
Operating lease agreement rent expense	4.9	$ 4.8	$ 3.8
Non cancellable purchase obligations	$ 17.7

Number of operating leases.

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- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

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- References

No definition available.

+ Details

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- Definition

For a classified balance sheet, the cumulative difference between the rental income or payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense, by the lessor or lessee, respectively, more than one year after the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.26(c))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 25
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77902458&loc=d3e39927-112707

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41499-112717

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant