Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair value hierarchy level 1 to level 2 transfers amount	$ 0		$ 0
Fair value hierarchy level 2 to level 1 transfers amount	0		0
Non-marketable equity securities					$ 400,000
Remeasurements or impairment losses on non-marketable equity securities	$ 0	$ 0	$ 0	$ 0

Non-marketable equity securities had carrying value.

No definition available.

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- Definition

Remeasurements or impairment losses on non-marketable equity securities.

+ References

No definition available.

+ Details

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- Definition

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

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- Definition

Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

+ References

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- References

No definition available.

+ Details

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