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

Costs incurred related to mine development in the current period.

No definition available.

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