Accrued Severance Benefits - Future Benefits Payments to Employees (Detail) $ in Thousands	Mar. 31, 2022 USD ($)
Postemployment Benefits [Abstract]
Remainder of 2022	$ 253
2023	631
2024	923
2025	1,505
2026	2,183
2027	1,746
2028 – 2032	$ 20,679

Post Employment Benefit Payments Five Fiscal Years Thereafter.

No definition available.

Name:	mx_PostEmploymentBenefitPaymentsFiveFiscalYearsThereafter
Namespace Prefix:	mx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant