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v3.20.2

NET SALES - Payment Terms (Details) | 9 Months Ended
--- | ---
Sep. 30, 2020
Minimum |
Net sales: |
Revenue satisfaction period | 7 days
Maximum |
Net sales: |
Revenue satisfaction period | 10 days

X
- Definition The satisfaction period of revenue remaining performance obligation. + References No definition available. + Details
Name: | mpx_RevenueRemainingPerformanceObligationSatisfactionPeriod
Namespace Prefix: | mpx_
Data Type: | xbrli:durationItemType
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_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |