The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives and The noncash expense charged against earnings to recognize the consumption of natural resources that are not part of an entity's cost of goods sold.

No definition available.

+ Details

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- Definition

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.14)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 14

-Article 5

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- Definition

Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.13)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.13)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 13

-Subparagraph a

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 8

-Article 7

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Property, Plant and Equipment (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 2,174.2us-gaap_PropertyPlantAndEquipmentGross	$ 1,282.3us-gaap_PropertyPlantAndEquipmentGross
Less: accumulated depreciation and depletion	(992.1)	(976.2)
Property, plant and equipment, net	1,182.1us-gaap_PropertyPlantAndEquipmentNet	306.1us-gaap_PropertyPlantAndEquipmentNet
Depreciation and depletion expense	76.6mtx_DepreciationAndDepletionExpense	44.7mtx_DepreciationAndDepletionExpense	48.7mtx_DepreciationAndDepletionExpense
Mineral rights and reserves [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	575.9	39.6
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	44.9	24.1
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	198.2	145.7
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,121.5	956.0
Furniture and fixtures and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	153.1	88.3
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 80.6	$ 28.6