Fair Value Measurements - Additional Information (Detail) - USD ($)		3 Months Ended	9 Months Ended
Oct. 15, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases of financial assets		$ 0	$ 0	$ 0	$ 0
Sales of financial assets		0	0	0	0
Maturities of financial assets		0	0	0	0
Transfer of financial asset into level 3 of fair value		0	0	0	0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized gains		0	0	0	0
Unrealized losses		$ 0	$ 0	$ 0	$ 0
Exclusive License Agreement [Member] \| Vifor International Ltd. [Member] \| Subsequent Event [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Non-refundable, non-creditable upfront payment	$ 100,000,000
Purchase of common stock value	$ 50,000,000
Common stock, shares issued	2,939,552

Revenue performance obligation upfront payment received.

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- Definition

Amount of unrealized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Section 50
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Amount of unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfer of financial instrument classified as an asset into (out of) level 3 of the fair value hierarchy.

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No definition available.

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Number of new stock issued during the period.

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Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

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