This element represents the amount of aggregate service charges.

No definition available.

Name:	mpx_AggregateServiceCharges
Namespace Prefix:	mpx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents joint venture ownership interest percentage.

+ References

No definition available.

+ Details

Name:	mpx_JointVentureOwnershipInterestPercentage
Namespace Prefix:	mpx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents rent and allocable expenses incurred during the period.

+ References

No definition available.

+ Details

Name:	mpx_RentAndAllocableShareOfFixedCost
Namespace Prefix:	mpx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount for accounts payable to related parties.

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-Subparagraph (SX 210.7-03.17)
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+ Details

Name:	us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow associated with the investment in or advances to an entity in which the reporting entity shares control of the entity with another party or group.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireInterestInJointVenture
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Receivables to be collected from (obligations owed to) related parties, net as of the balance sheet date where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth.

+ References

+ Details

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

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

- Definition

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mpx_RpcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=mpx_LimitedLiability255RCLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=mpx_TransitionSupportServicesAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_BoardOfDirectorsChairmanMember
Namespace Prefix:
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Balance Type:
Period Type:

RELATED PARTY TRANSACTIONS (Details) - USD ($)	1 Months Ended	12 Months Ended
RELATED PARTY TRANSACTIONS (Details) - USD ($)	Jan. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
RPC \| 255 RC, LLC
Related Party Transaction [Line Items]
Joint venture ownership interest percentage	50.00%
Investment in joint venture	$ 2,554,000
Operating lease agreement term	5 years
Rent and allocable fixed cost for corporate aircraft		$ 159,000	$ 159,000	$ 157,000
Payable due to related party		1,000,000.0	800,000
RPC \| Transition Support Services Agreement
Related Party Transaction [Line Items]
Aggregate service charges paid		865,000	873,000	$ 849,000
Receivable (payable) due from (to) related party		$ (56,000)	$ (28,000)
Chairman of Board and Director
Related Party Transaction [Line Items]
Voting power (in percent)		50.00%