Fair Value Measurements and Marketable Securities - Summary of Aggregate fair values of marketable securities with unrealized losses and gains (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Debt Securities, Available-for-Sale [Line Items]
Aggregate fair value of marketable securities in a continuous loss position for less than twelve months	$ 218,350	$ 15,449
Aggregate fair value of marketable securities in a continuous loss position for more than twelve months	0	1,951
Aggregate fair value of marketable securities in unrealized gain position	166,793	446,368
Total marketable securities	$ 385,143	$ 463,768

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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+ Details

4D Molecular Therapeutics, Inc. 10-Q