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MARKETABLE SECURITIES - Gross unrealized gains (losses) on marketable securities (Details 1) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized Gains	$ 119mpx_AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInAOCI	$ 122mpx_AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInAOCI
Gross unrealized (Losses)	(12)mpx_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInAOCI	(37)mpx_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInAOCI
Municipal Obligations
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized Gains	99mpx_AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInAOCI / us-gaap_DebtSecurityAxis = us-gaap_MunicipalNotesMember	121mpx_AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInAOCI / us-gaap_DebtSecurityAxis = us-gaap_MunicipalNotesMember
Gross unrealized (Losses)	(10)mpx_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInAOCI / us-gaap_DebtSecurityAxis = us-gaap_MunicipalNotesMember	(31)mpx_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInAOCI / us-gaap_DebtSecurityAxis = us-gaap_MunicipalNotesMember
Corporate obligations
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized Gains	20mpx_AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInAOCI / us-gaap_DebtSecurityAxis = us-gaap_CorporateDebtSecuritiesMember	1mpx_AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInAOCI / us-gaap_DebtSecurityAxis = us-gaap_CorporateDebtSecuritiesMember
Gross unrealized (Losses)	$ (2)mpx_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInAOCI / us-gaap_DebtSecurityAxis = us-gaap_CorporateDebtSecuritiesMember	$ (6)mpx_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInAOCI / us-gaap_DebtSecurityAxis = us-gaap_CorporateDebtSecuritiesMember

X

- Definition

Amount of accumulated pre-tax unrealized gains on investments in available-for-sale securities that are recognized in Accumulated Other Comprehensive Income (AOCI).

+ References

No definition available.

+ Details

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X

- Definition

Amount of accumulated pre-tax unrealized loss before deducting unrealized gain on investments in available- for-sale securities recognized in Accumulated Other Comprehensive Income (AOCI).

+ References

No definition available.

+ Details

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X

- Details

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X

- Details

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