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MARKETABLE SECURITIES (Detail Textuals)	6 Months Ended
	Jun. 30, 2018
Schedule of Available-for-sale Securities [Line Items]
Period of current marketable securities	less than 12 months
Period of non-current marketable securities	greater than 12 months
Maturity term of non-current marketable securities	between 2019 and 2047
Municipal Obligations | AA- or higher
Schedule of Available-for-sale Securities [Line Items]
Period of maturity debt obligations	less than one year to over 20 years
Corporate obligations | BBB+ or higher
Schedule of Available-for-sale Securities [Line Items]
Period of maturity debt obligations	from one to five years

X

- Definition

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

+ References

No definition available.

+ Details

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

X

- Definition

This element represents period of current marketable securities.

+ References

No definition available.

+ Details

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

X

- Definition

Represents the maturity period of marketable securities.

+ References

No definition available.

+ Details

Name:	mpx_PeriodOfMaturityOfMarketableSecurities
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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsAAMinusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsBBBPlusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: