Amount of corporate headquarter items not allocated to segments.

No definition available.

Name:	mtx_UnallocatedCorporateExpenses
Namespace Prefix:	mtx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

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

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e1043-128460

+ Details

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

+ Details

Name:	us-gaap_DepreciationDepletionAndAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(1)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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

- Definition

The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

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

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

+ Details

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

- Definition

The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

+ Details

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

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mtx_PerformanceMaterialsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mtx_SpecialtyMineralsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mtx_RefractoriesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mtx_EnergyServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidationItemsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidationItemsAxis=us-gaap_CorporateNonSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Segment and Related Information, Reportable Segments (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 29, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jul. 01, 2018 USD ($)	Apr. 01, 2018 USD ($)	Dec. 31, 2019 USD ($) Segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment and Related Information [Abstract]
Number of reportable segments \| Segment									4
Segment Reporting Information [Abstract]
Net sales	$ 440.2	$ 449.3	$ 463.8	$ 437.7	$ 447.5	$ 464.1	$ 464.7	$ 431.3	$ 1,791.0	$ 1,807.6	$ 1,675.7
Income from operations	47.7	53.5	45.5	62.0	62.3	68.2	62.8	62.6	208.7	255.9	244.4
Depreciation, depletion and amortization									98.4	94.3	91.0
Segment assets	3,112.6				3,087.1				3,112.6	3,087.1	2,970.4
Capital expenditures									65.0	75.9	76.7
Income from Operations before Provision (Benefit) for Taxes on Income [Abstract]
Acquisition related transaction and integration costs									0.0	(1.7)	(3.4)
Unallocated corporate expenses									(19.1)	(4.5)	(6.7)
Consolidated income from operations	47.7	53.5	45.5	62.0	62.3	68.2	62.8	62.6	208.7	255.9	244.4
Non-operating deductions, net									(51.4)	(51.8)	(53.5)
Income from operations before provision (benefit) for taxes on income									157.3	204.1	190.9
Performance Materials [Member]
Segment Reporting Information [Abstract]
Net sales	201.4	207.3	215.4	199.2	206.8	219.5	214.5	187.3	823.3	828.1	734.8
Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net sales	141.8	143.1	145.1	144.4	142.5	146.3	150.9	149.6	574.4	589.3	584.8
Refractories [Member]
Segment Reporting Information [Abstract]
Net sales	73.4	73.4	77.5	73.8	77.9	79.1	79.6	75.3	298.1	311.9	279.4
Energy Services [Member]
Segment Reporting Information [Abstract]
Net sales	23.6	$ 25.5	$ 25.8	$ 20.3	20.3	$ 19.2	$ 19.7	$ 19.1	95.2	78.3	76.7
Reportable Segments [Member]
Segment Reporting Information [Abstract]
Net sales									1,791.0	1,807.6	1,675.7
Income from operations									227.8	262.1	254.5
Depreciation, depletion and amortization									98.4	94.3	91.0
Segment assets	3,031.0				3,038.6				3,031.0	3,038.6	2,927.0
Capital expenditures									64.9	74.7	76.1
Income from Operations before Provision (Benefit) for Taxes on Income [Abstract]
Consolidated income from operations									227.8	262.1	254.5
Reportable Segments [Member] \| Performance Materials [Member]
Segment Reporting Information [Abstract]
Net sales									823.3	828.1	734.8
Income from operations									97.1	116.8	119.7
Depreciation, depletion and amortization									43.6	41.1	40.5
Segment assets	2,091.2				2,119.7				2,091.2	2,119.7	1,989.6
Capital expenditures									16.8	22.4	33.1
Income from Operations before Provision (Benefit) for Taxes on Income [Abstract]
Consolidated income from operations									97.1	116.8	119.7
Reportable Segments [Member] \| Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net sales									574.4	589.3	584.8
Income from operations									83.1	95.4	88.9
Depreciation, depletion and amortization									40.4	38.2	35.5
Segment assets	525.1				511.9				525.1	511.9	519.4
Capital expenditures									37.7	42.4	32.6
Income from Operations before Provision (Benefit) for Taxes on Income [Abstract]
Consolidated income from operations									83.1	95.4	88.9
Reportable Segments [Member] \| Refractories [Member]
Segment Reporting Information [Abstract]
Net sales									298.1	311.9	279.4
Income from operations									39.8	45.4	39.8
Depreciation, depletion and amortization									7.0	6.6	6.8
Segment assets	293.2				296.6				293.2	296.6	307.4
Capital expenditures									5.7	5.0	5.9
Income from Operations before Provision (Benefit) for Taxes on Income [Abstract]
Consolidated income from operations									39.8	45.4	39.8
Reportable Segments [Member] \| Energy Services [Member]
Segment Reporting Information [Abstract]
Net sales									95.2	78.3	76.7
Income from operations									7.8	4.5	6.1
Depreciation, depletion and amortization									7.4	8.4	8.2
Segment assets	121.5				110.4				121.5	110.4	110.6
Capital expenditures									4.7	4.9	4.5
Income from Operations before Provision (Benefit) for Taxes on Income [Abstract]
Consolidated income from operations									7.8	4.5	6.1
Corporate [Member]
Segment Reporting Information [Abstract]
Segment assets	$ 81.6				$ 48.5				81.6	48.5	43.4
Capital expenditures									$ 0.1	$ 1.2	$ 0.6