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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.

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

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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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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.

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Segment and Related Information, Reportable Segments (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jul. 01, 2018 USD ($)	Apr. 01, 2018 USD ($)	Dec. 31, 2017 USD ($)	Oct. 01, 2017 USD ($)	Jul. 02, 2017 USD ($)	Apr. 02, 2017 USD ($)	Dec. 31, 2018 USD ($) Segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Segment and Related Information [Abstract]
Number of reportable segments \| Segment									4
Segment Reporting Information [Abstract]
Net sales	$ 447.5	$ 464.1	$ 464.7	$ 431.3	$ 432.1	$ 424.5	$ 414.1	$ 405.0	$ 1,807.6	$ 1,675.7	$ 1,638.0
Income from operations	62.3	68.2	62.8	62.6	46.1	67.2	69.0	62.1	255.9	244.4	223.9
Depreciation, depletion and amortization									94.3	91.0	91.9
Segment assets	3,087.1				2,970.4				3,087.1	2,970.4	2,863.4
Capital expenditures									75.9	76.7	62.4
Income from operations before provision (benefit) for taxes on income [Abstract]
Acquisition related transaction and integration costs									(1.7)	(3.4)	(8.0)
Unallocated corporate expenses									(4.5)	(6.7)	(3.0)
Consolidated income from operations	62.3	68.2	62.8	62.6	46.1	67.2	69.0	62.1	255.9	244.4	223.9
Non-operating deductions, net									(51.8)	(53.5)	(53.6)
Income from operations before provision (benefit) for taxes on income									204.1	190.9	170.3
Performance Materials [Member]
Segment Reporting Information [Abstract]
Net sales	206.8	219.5	214.5	187.3	195.8	188.8	180.3	169.9	828.1	734.8	686.1
Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net sales	142.5	146.3	150.9	149.6	143.9	147.7	147.0	146.2	589.3	584.8	591.5
Refractories [Member]
Segment Reporting Information [Abstract]
Net sales	77.9	79.1	79.6	75.3	71.3	69.0	68.9	70.2	311.9	279.4	274.5
Energy Services [Member]
Segment Reporting Information [Abstract]
Net sales	20.3	$ 19.2	$ 19.7	$ 19.1	21.1	$ 19.0	$ 17.9	$ 18.7	78.3	76.7	85.9
Reportable Segments [Member]
Segment Reporting Information [Abstract]
Net sales									1,807.6	1,675.7	1,638.0
Income from operations									262.1	254.5	234.9
Depreciation, depletion and amortization									94.3	91.0	91.9
Segment assets	3,038.6				2,927.0				3,038.6	2,927.0	2,821.9
Capital expenditures									74.7	76.1	60.5
Income from operations before provision (benefit) for taxes on income [Abstract]
Consolidated income from operations									262.1	254.5	234.9
Reportable Segments [Member] \| Performance Materials [Member]
Segment Reporting Information [Abstract]
Net sales									828.1	734.8	686.1
Income from operations									116.8	119.7	121.1
Depreciation, depletion and amortization									41.1	40.5	38.9
Segment assets	2,119.7				1,989.6				2,119.7	1,989.6	1,942.1
Capital expenditures									22.4	33.1	12.8
Income from operations before provision (benefit) for taxes on income [Abstract]
Consolidated income from operations									116.8	119.7	121.1
Reportable Segments [Member] \| Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net sales									589.3	584.8	591.5
Income from operations									95.4	88.9	102.7
Depreciation, depletion and amortization									38.2	35.5	34.9
Segment assets	511.9				519.4				511.9	519.4	491.7
Capital expenditures									42.4	32.6	40.4
Income from operations before provision (benefit) for taxes on income [Abstract]
Consolidated income from operations									95.4	88.9	102.7
Reportable Segments [Member] \| Refractories [Member]
Segment Reporting Information [Abstract]
Net sales									311.9	279.4	274.5
Income from operations									45.4	39.8	37.0
Depreciation, depletion and amortization									6.6	6.8	6.9
Segment assets	296.6				307.4				296.6	307.4	283.4
Capital expenditures									5.0	5.9	5.9
Income from operations before provision (benefit) for taxes on income [Abstract]
Consolidated income from operations									45.4	39.8	37.0
Reportable Segments [Member] \| Energy Services [Member]
Segment Reporting Information [Abstract]
Net sales									78.3	76.7	85.9
Income from operations									4.5	6.1	(25.9)
Depreciation, depletion and amortization									8.4	8.2	11.2
Segment assets	110.4				110.6				110.4	110.6	104.7
Capital expenditures									4.9	4.5	1.4
Income from operations before provision (benefit) for taxes on income [Abstract]
Consolidated income from operations									4.5	6.1	(25.9)
Corporate [Member]
Segment Reporting Information [Abstract]
Segment assets	$ 48.5				$ 43.4				48.5	43.4	41.5
Capital expenditures									$ 1.2	$ 0.6	$ 1.9