Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Cash Equivalents and Short-term Investments [Abstract]
Short-term investments	$ 0.8us-gaap_ShortTermInvestments	$ 15.8us-gaap_ShortTermInvestments
Unrealized holding gains and losses on short-term bank investments	0us-gaap_UnrealizedGainLossOnInvestments
Trade Accounts Receivable [Abstract]
Past due threshold for individual collectability review	90 days
Property, Plant and Equipment [Abstract]
Initial term of long term evergreen contracts	10 years
Investment in joint ventures [Abstract]
Equity method investment	7.4us-gaap_EquityMethodInvestments
Cost Method Investments	$ 7.5us-gaap_CostMethodInvestments
Buildings [Member]
Property, Plant and Equipment [Abstract]
Annual rates of depreciation, minimum (in hundredths)	3.00%
Annual rates of depreciation, maximum (in hundredths)	6.67%
Machinery and equipment [Member]
Property, Plant and Equipment [Abstract]
Annual rates of depreciation, minimum (in hundredths)	6.67%
Annual rates of depreciation, maximum (in hundredths)	12.50%
Furniture and fixtures [Member]
Property, Plant and Equipment [Abstract]
Annual rates of depreciation, minimum (in hundredths)	8.00%
Annual rates of depreciation, maximum (in hundredths)	12.50%
Computer equipment and software-related assets [Member]
Property, Plant and Equipment [Abstract]
Annual rates of depreciation, minimum (in hundredths)	12.50%
Annual rates of depreciation, maximum (in hundredths)	25.00%
PCC production facilities [Member]
Property, Plant and Equipment [Abstract]
Estimated useful life	15 years
Machinery and equipment for natural stone mining and processing plants and chemical plants [Member]
Property, Plant and Equipment [Abstract]
Estimated useful life	15 years

Maximum annual depreciation rate.

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Minimum annual depreciation rate.

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- Definition

The initial length of time that the company's long-term evergreen contracts are in effect. Sales of PCC (precipitated calcium carbonate) are predominantly pursuant to long-term evergreen contracts.

+ References

No definition available.

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The length of time for which a receivable is past due that will trigger an individual review for collectability.

+ References

No definition available.

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- Definition

Amount, after adjustment, of cost-method investment. Adjustments include, but are not limited to, dividends received in excess of earnings after date of investment that are considered a return of investment and other than temporary impairments.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.12)

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 325

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6872867&loc=d3e40691-111596

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 325

-SubTopic 20

-Section 35

-Paragraph 2

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This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

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- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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