v3.7.0.1

Receivables - Receivables Available for Sale and Sold under Factoring Agreements (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Available for sale	$ 44.3	$ 47.3
Sold	$ 36.5	$ 37.7

X

- Definition

The amount of outstanding receivables that had been sold as of reporting date.

+ References

No definition available.

+ Details

Name:	mpg_TradeReceivablesSoldAmount
Namespace Prefix:	mpg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- References

No definition available.

+ Details

Name:	us-gaap_ReceivablesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The face amount of accounts receivable that will be sold to other entities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

+ Details

Name:	us-gaap_TradeReceivablesHeldForSaleAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant