Amount of corporate headquarter items not allocated to segments.

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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
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- 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.

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-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
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- 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.

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(1)(i))
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- 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).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (SX 210.5-03.7)
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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.

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No definition available.

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

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No definition available.

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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.

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- References

No definition available.

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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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-Publisher FASB
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-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
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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.

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No definition available.

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Segment and Related Information (Details) $ in Millions	3 Months Ended								12 Months Ended
Segment and Related Information (Details) $ in Millions	Dec. 31, 2017 USD ($)	Oct. 01, 2017 USD ($)	Jul. 02, 2017 USD ($)	Apr. 02, 2017 USD ($)	Dec. 31, 2016 USD ($)	Oct. 02, 2016 USD ($)	Jul. 03, 2016 USD ($)	Apr. 03, 2016 USD ($)	Dec. 31, 2017 USD ($) Segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment and Related Information [Abstract]
Number of reportable segments \| Segment									4
Segment Reporting Information [Line Items]
Net sales	$ 432.1	$ 424.5	$ 414.1	$ 405.0	$ 401.3	$ 399.5	$ 427.0	$ 410.2	$ 1,675.7	$ 1,638.0	$ 1,797.6
Income from operations	45.7	66.8	68.5	61.7	56.5	67.3	39.5	57.6	242.7	220.9	200.3
Depreciation, depletion and amortization									91.0	91.9	98.3
Segment assets	2,970.4				2,863.4				2,970.4	2,863.4	2,980.0
Capital expenditures									76.7	62.4	86.0
Income from operations before provision (benefit) for taxes on income [Abstract]
Acquisition related transaction and integration costs									(3.4)	(8.0)	(11.8)
Unallocated corporate expenses									(8.4)	(6.0)	(7.0)
Consolidated income from operations	45.7	66.8	68.5	61.7	56.5	67.3	39.5	57.6	242.7	220.9	200.3
Non-operating deductions, net									(51.8)	(50.6)	(67.7)
Income from continuing operations before provision (benefit) for taxes on income									190.9	170.3	132.6
Specialty Minerals [Member]
Segment Reporting Information [Line Items]
Net sales	143.9	147.7	147.0	146.2	138.0	147.3	150.6	155.6
Performance Materials [Member]
Segment Reporting Information [Line Items]
Net sales	195.8	188.8	180.3	169.9	175.0	169.0	182.5	159.6
Refractories [Member]
Segment Reporting Information [Line Items]
Net sales	71.3	69.0	68.9	70.2	68.0	63.4	73.9	69.2
Energy Services [Member]
Segment Reporting Information [Line Items]
Net sales	21.1	$ 19.0	$ 17.9	$ 18.7	20.3	$ 19.8	$ 20.0	$ 25.8
Reportable Segments [Member]
Segment Reporting Information [Line Items]
Net sales									1,675.7	1,638.0	1,797.6
Income from operations									254.5	234.9	219.1
Depreciation, depletion and amortization									91.0	91.9	98.3
Segment assets	2,927.0				2,821.9				2,927.0	2,821.9	2,918.1
Capital expenditures									76.1	60.5	85.2
Income from operations before provision (benefit) for taxes on income [Abstract]
Consolidated income from operations									254.5	234.9	219.1
Reportable Segments [Member] \| Specialty Minerals [Member]
Segment Reporting Information [Line Items]
Net sales									584.8	591.5	624.6
Income from operations									88.9	102.7	100.8
Depreciation, depletion and amortization									35.5	34.9	34.0
Segment assets	519.4				491.7				519.4	491.7	505.3
Capital expenditures									32.6	40.4	51.9
Income from operations before provision (benefit) for taxes on income [Abstract]
Consolidated income from operations									88.9	102.7	100.8
Reportable Segments [Member] \| Performance Materials [Member]
Segment Reporting Information [Line Items]
Net sales									734.8	686.1	694.9
Income from operations									119.7	121.1	118.4
Depreciation, depletion and amortization									40.5	38.9	39.4
Segment assets	1,989.6				1,942.1				1,989.6	1,942.1	1,965.4
Capital expenditures									33.1	12.8	11.1
Income from operations before provision (benefit) for taxes on income [Abstract]
Consolidated income from operations									119.7	121.1	118.4
Reportable Segments [Member] \| Refractories [Member]
Segment Reporting Information [Line Items]
Net sales									279.4	274.5	295.9
Income from operations									39.8	37.0	27.8
Depreciation, depletion and amortization									6.8	6.9	7.5
Segment assets	307.4				283.4				307.4	283.4	292.7
Capital expenditures									5.9	5.9	11.1
Income from operations before provision (benefit) for taxes on income [Abstract]
Consolidated income from operations									39.8	37.0	27.8
Reportable Segments [Member] \| Energy Services [Member]
Segment Reporting Information [Line Items]
Net sales									76.7	85.9	182.2
Income from operations									6.1	(25.9)	(27.9)
Depreciation, depletion and amortization									8.2	11.2	17.4
Segment assets	110.6				104.7				110.6	104.7	154.7
Capital expenditures									4.5	1.4	11.1
Income from operations before provision (benefit) for taxes on income [Abstract]
Consolidated income from operations									6.1	(25.9)	(27.9)
Corporate [Member]
Segment Reporting Information [Line Items]
Segment assets	$ 43.4				$ 41.5				43.4	41.5	61.9
Capital expenditures									$ 0.6	$ 1.9	$ 0.8