Other long-term liabilities - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Subclassifications of assets, liabilities and equities [abstract]
Undiscounted amount of estimated cash flows required to settle liabilities	$ 95.4	$ 64.1

Undiscounted Estimated Cash Flows Required To Settle Liabilities

No definition available.

Name:	mx_UndiscountedEstimatedCashFlowsRequiredToSettleLiabilities
Namespace Prefix:	mx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration