Subsequent Event - Additional Information (Detail) - Co-Development and Collaboration Agreement - Strata Oncology, Inc - Subsequent Event $ in Millions	Apr. 30, 2019 USD ($) shares
Subsequent Event [Line Items]
Development milestone payable \| $	$ 2.5
Number of restricted shares of common stock issued \| shares	1,257,651

Total number of shares issued during the period, including shares forfeited, as a result of Restricted Stock Awards.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration