Stockholders' Equity - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Class of Stock [Line Items]
Common stock, voting rights	one
Stock options, exercisable (in shares)	3,116,514
Total intrinsic value of options exercised	$ 200	$ 800
Cost not yet recognized	$ 1,000
Stock compensation not yet recognized, vesting period	8 months 12 days
Stock-based compensation	$ 2,781	2,246
General and administrative expense
Class of Stock [Line Items]
Stock-based compensation	2,100	1,400
Research and development expense
Class of Stock [Line Items]
Stock-based compensation	$ 600	800
Stock Plans
Class of Stock [Line Items]
Stock option plan, exercisable period	4 years
Stock Plans | Share-based payment arrangement, nonemployee
Class of Stock [Line Items]
Stock option plan, exercisable period	10 years
Stock Plans | One year from the vesting commencement date
Class of Stock [Line Items]
Stock option plan, vesting percentage	25.00%
Option vesting period	1 year
Stock Plans | More than one year from vesting commencement date
Class of Stock [Line Items]
Stock option plan, vesting percentage	2.778%
Employee Stock | Employee Stock Purchase Plan
Class of Stock [Line Items]
Purchase price of common stock	85.00%
Number of shares authorized (in shares)			5,639,944		1,846,710
Evergreen shares reserve feature period	10 years
Increase in shares authorized	1.00%
Increase in number of shares of authorized common stock (in shares)	3,693,420
Employee Stock | Stock Plans
Class of Stock [Line Items]
Common stock, shares reserved (in shares)	30,004,203		28,761,816
Stock options available for grant (in shares)	10,229,786
Employee Stock | 2021 Equity Incentive Plan
Class of Stock [Line Items]
Number of shares authorized (in shares)				18,467,109
Evergreen shares reserve feature period	10 years
Increase in shares authorized	5.00%
Maximum percentage of share reserve, outstanding diluted stock	15.00%
Number of additional shares authorized (in shares)	1,242,387
RSU awards
Class of Stock [Line Items]
Option vesting period	2 years 1 month 6 days
Total intrinsic value of options exercised	$ 100	$ 400
Number of RSU awards vested (in shares)	212,633
Issuance of common shares (in shares)	64,451
Vested (in shares)	212,633
Unvested outstanding (in shares)	11,053,204		10,927,261
Share-based payment arrangement expense	$ 9,200
RSU awards | Stock Plans
Class of Stock [Line Items]
Option vesting period	3 years
Requisite service period	3 years
RSU awards | Stock Plans | Tranche two
Class of Stock [Line Items]
Stock option plan, vesting percentage	33.30%
RSU awards | Stock Plans | Tranche three
Class of Stock [Line Items]
Stock option plan, vesting percentage	33.30%
RSU awards | Stock Plans | Tranche one
Class of Stock [Line Items]
Stock option plan, vesting percentage	33.30%
RSU awards | 2021 Equity Incentive Plan
Class of Stock [Line Items]
Stock compensation not yet recognized, vesting period	3 years
Cost not yet recognized, excluding options	$ 15,400
Performance-based stock awards
Class of Stock [Line Items]
Unvested outstanding (in shares)	1,794,893		2,118,843
Performance-based stock awards | Tranche one
Class of Stock [Line Items]
Unvested outstanding (in shares)	554,534
Performance-based stock awards | Stock Plans | Minimum
Class of Stock [Line Items]
Stock option plan, vesting percentage	0.00%
Performance-based stock awards | Stock Plans | Maximum
Class of Stock [Line Items]
Stock option plan, vesting percentage	300.00%
Performance-based stock awards | 2021 Equity Incentive Plan
Class of Stock [Line Items]
Vested (in shares)	27,600
Performance-Based Stock
Class of Stock [Line Items]
Shares issued (in shares)	455,368