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EMPLOYEE BENEFIT PLANS (Detail Textuals 1) - Supplemental Executive Retirement Plan (SERP) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Supplemental executive retirement plan, assets	$ 6,264,000		$ 6,031,000
Trading gains related to SERP	$ 211,000	$ 300,000

X

- Definition

This element represents the amount of trading gains and losses of plan assets under the defined benefit plan.

+ References

No definition available.

+ Details

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Namespace Prefix:	mpx_
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Balance Type:	credit
Period Type:	duration

X

- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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Balance Type:	debit
Period Type:	instant

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

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- Details

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Namespace Prefix:
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Balance Type:
Period Type: