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Significant Accounting Policies - Mineral Resources and Mine Development (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Accounting Policies [Abstract]
Cost of mine development	$ 12.9

X

- Definition

Costs incurred related to mine development in the current period.

+ References

No definition available.

+ Details

Name:	mtrn_CostOfMineDevelopment
Namespace Prefix:	mtrn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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- References

No definition available.

+ Details

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