Accrued Severance Benefits - Additional Information (Detail)	Sep. 30, 2014
Compensation and Retirement Disclosure [Abstract]
Eligible employees for severance benefits	98.00%

Employees eligible for severance benefits percentage.

No definition available.

Name:	mx_EmployeesEligibleForSeveranceBenefitsPercentage
Namespace Prefix:	mx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant