Fair Value Measurements (Details) - Mayville Engineering Company, Inc. 401(k) Plan - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Fair Value Measurements
Investments at fair value	$ 184,242	$ 156,073
Mutual funds
Fair Value Measurements
Investments at fair value	139,903	122,967
Mutual funds \| Level 1
Fair Value Measurements
Investments at fair value	139,903	122,967
Company stock
Fair Value Measurements
Investments at fair value	44,339	33,106
Company stock \| Level 1
Fair Value Measurements
Investments at fair value	$ 44,339	$ 33,106

Fair value of investment, excluding plan interest in master trust, held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, derivative, investment measured at net asset value per share as practical expedient, and insurance contract not meeting fully-benefit responsive investment criteria.

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+ Details

- Definition

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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