Organization and Description of Business - Narrative (Detail) $ / shares in Units, $ in Millions		1 Months Ended
	May 22, 2020	Jun. 30, 2020 USD ($) $ / shares shares	Mar. 31, 2021 shares	Dec. 31, 2020 shares
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reverse stock split, conversion ratio	0.13986014
Common stock, shares issued (in shares)			35,748,336	35,552,795
Initial Public Offering
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reverse stock split, conversion ratio		7.15
Initial public offering, shares issued (in shares)		10,350,000
Share price of shares issued in initial public offering (USD per share) | $ / shares		$ 16.00
Proceeds from the initial public offering | $		$ 148.3
Underwriting discounts, commissions and offering expenses | $		$ 5.7
Convertible preferred stock converted into common shares (in shares)		160,389,279
Reclassification of convertible preferred stock into additional paid in capital upon initial public offering | $		$ 238.3
Initial Public Offering | Underwriters
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Initial public offering, shares issued (in shares)		1,350,000
Initial Public Offering | Common Stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Initial public offering, shares issued (in shares)		9,000,000
Private Placement | Novartis
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common stock, shares issued (in shares)		625,000
Share price (USD per share) | $ / shares		$ 16.00
Proceeds from issuance of common stock | $		$ 10.0
Private Placement | Pliant Therapeutics, Inc. | Novartis
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Percentage of noncontrolling ownership		6.10%