Foreign Currency Gain (Loss), Net - Additional Information (Detail) In Millions, unless otherwise specified	Mar. 31, 2015 USD ($)	Mar. 31, 2015 KRW	Dec. 31, 2014 KRW
Foreign Currency Transaction [Abstract]
Exchange rates using first base rate		1,105.0	1,099.2
Intercompany loan balance	$ 762mx_IntercompanyLoan

Foreign exchange rate used to translate amounts denominated in functional currency to reporting currency.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 830

-SubTopic 30

-Section S99

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6897108&loc=SL6897125-166521

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant