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Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016
Cash Equivalents and Short-term Investments [Abstract] |  |
Short-term investments | $ 2.7 | $ 2.0
Unrealized holding gains and losses on short-term bank investments | $ 0.0 |
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 | $ 16.1 |
Cost method investment | $ 0.0 |
Buildings [Member] | Minimum [Member] |  |
Property, Plant and Equipment [Abstract] |  |
Annual rates of depreciation | 3.00% |
Buildings [Member] | Maximum [Member] |  |
Property, Plant and Equipment [Abstract] |  |
Annual rates of depreciation | 6.67% |
Machinery and Equipment [Member] | Minimum [Member] |  |
Property, Plant and Equipment [Abstract] |  |
Annual rates of depreciation | 6.67% |
Machinery and Equipment [Member] | Maximum [Member] |  |
Property, Plant and Equipment [Abstract] |  |
Annual rates of depreciation | 12.50% |
Furniture and Fixtures [Member] | Minimum [Member] |  |
Property, Plant and Equipment [Abstract] |  |
Annual rates of depreciation | 8.00% |
Furniture and Fixtures [Member] | Maximum [Member] |  |
Property, Plant and Equipment [Abstract] |  |
Annual rates of depreciation | 12.50% |
Computer Equipment and Software-related Assets [Member] | Minimum [Member] |  |
Property, Plant and Equipment [Abstract] |  |
Annual rates of depreciation | 12.50% |
Computer Equipment and Software-related Assets [Member] | Maximum [Member] |  |
Property, Plant and Equipment [Abstract] |  |
Annual rates of depreciation | 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 |

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- Definition The initial length of time that the company's long-term evergreen contracts in effect. Sales of PCC (precipitated calcium carbonate) are predominantly pursuant to long-term evergreen contracts, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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