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MARKETABLE SECURITIES (Detail Textuals)	9 Months Ended
	Sep. 30, 2012
Municipal obligations | A1/P1 or higher Rating
Schedule of Available-for-sale Securities [Line Items]
Period of maturity of municipal notes	less than 12 months to over 10 years
Corporate obligations | BBB or higher Rating
Schedule of Available-for-sale Securities [Line Items]
Period of non-current marketable securities	2014 and 2048
Corporate obligations | BBB or higher Rating | Maximum
Schedule of Available-for-sale Securities [Line Items]
Period of debentures and notes issued	4 years
Corporate obligations | BBB or higher Rating | Minimum
Schedule of Available-for-sale Securities [Line Items]
Period of debentures and notes issued	2 years

X

- Definition

Describe the approximate term of the debentures and notes issued provided by the company.

+ References

No definition available.

+ Details

Name:	mpx_PeriodOfDebenturesAndNotesIssued
Namespace Prefix:	mpx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Describe the approximate term of the municipal notes.

+ References

No definition available.

+ Details

Name:	mpx_PeriodOfMaturityOfMunicipalNotes
Namespace Prefix:	mpx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Describe the approximate term of the non-current marketable securities.

+ References

No definition available.

+ Details

Name:	mpx_PeriodOfNonCurrentMarketableSecurities
Namespace Prefix:	mpx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

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