Summary of Significant Accounting Policies - Income Taxes (Details)	Jun. 27, 2025
Accounting Policies [Abstract]
Minimum likelihood of tax benefits being recognized upon ultimate settlement	50.00%

Percentage Of Income Tax Examination Minimum Likelihood of Tax Benefits Being Realized Upon Settlement

No definition available.

Name:	mrcy_PercentageOfIncomeTaxExaminationMinimumLikelihoodOfTaxBenefitsBeingRealizedUponSettlement
Namespace Prefix:	mrcy_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	instant