Income Taxes	9 Months Ended
Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes: The Company’s effective income tax rate differs from the U.S. statutory federal income tax rate primarily due to U.S. statutory depletion, state income taxes (net of federal tax benefit), foreign income tax rate differentials, foreign mining taxes, domestic manufacturing deductions, interest expense recognition differences for book and tax purposes and a partial release of valuation allowance in connection with the acquisition of Produquímica. The Company’s effective rate is impacted by permanent tax deductions which have a less favorable impact as pretax income increases. During the nine months ended September 30, 2017, the Company determined it is more likely than not that a portion of its Brazilian deferred tax assets acquired in connection with the acquisition of Produquímica will be used to reduce taxable income. Based on current estimates of taxable income, the Company projects to release approximately $25 million of valuation allowances during the year ending December 31, 2017. For the nine months ended September 30, 2017, the Company included approximately $12 million of this valuation allowance release in the calculation of the estimated annual effective tax rate for the current fiscal year, and approximately $13 million as a discrete income tax benefit. The Company had $52.0 million and $53.6 million as of September 30, 2017, and December 31, 2016, respectively, of gross foreign federal net operating loss (“NOL”) carryforwards that have no expiration date. In addition, the Company had $10.8 million and $7.5 million as of September 30, 2017, and December 31, 2016, respectively, of gross foreign federal NOL carryforwards which expire beginning in 2033 and $1.3 million and $0.9 million as of September 30, 2017, and December 31, 2016, respectively, of tax-effected state NOL carryforwards which expire beginning in 2033. Canadian provincial tax authorities have challenged tax positions claimed by one of the Company’s Canadian subsidiaries and have issued tax reassessments for years 2002-2012. The reassessments are a result of ongoing audits and total $104.4 million, including interest through September 30, 2017. The Company disputes these reassessments and will continue to work with the appropriate authorities in Canada to resolve the dispute. Although the Company believes it has recorded an adequate reserve for this matter, there is a reasonable possibility that the ultimate resolution of this dispute, and any related disputes for other open tax years, may be materially higher or lower than the amounts the Company has reserved for such disputes. In connection with this dispute, local regulations require the Company to post security with the tax authority until the dispute is resolved. The Company has posted collateral in the form of a $63.6 million performance bond, has paid $35.2 million (most of which is recorded in other assets in its consolidated balance sheets) and the remaining balance of $5.6 million is expected to be addressed later this year, which is necessary to proceed with future appeals or litigation. In addition, Canadian federal and provincial taxing authorities had reassessed the Company for years 2004-2006, which had been previously settled by agreement among the Company, the Canada Revenue Agency and the Internal Revenue Service of the United States. The Company sought to enforce the agreement, which provided the basis upon which the returns were previously filed and settled. In July 2016, a trial commenced in the Tax Court of Canada with respect to the Canadian federal tax issues for these matters, and in March 2017, the Tax Court of Canada ruled in favor of the Company. The decision of the Tax Court of Canada was not appealed by the Canada Revenue Agency. As a result, the Company believes that reassessed Canadian tax, penalties and interest for the Company for years 2004-2006 of approximately $94.7 million are effectively resolved. The Company is in the process of having certain posted collateral returned in connection with the resolution of the dispute. The Company received Canadian income tax reassessments for years 2007-2008. The total amount of the reassessments, including penalties and interest through September 30, 2017, related to this matter is $37.2 million. The Company does not agree with these adjustments and is receiving assistance from the tax jurisdictions for relief from the impact of double taxation as available in the tax treaty between the U.S. and Canada. The Company has filed protective Notices of Objection and has posted collateral in the form of a $10.2 million performance bond and a $8.0 million bank letter guarantee, which is necessary to proceed with future appeals or litigation. Although the outcome of examinations by taxing authorities is uncertain, the Company believes it has adequately reserved for this matter. The Company expects that it will be required by local regulations to provide security for additional interest on the above unresolved disputed amounts and for any future reassessments issued by these Canadian tax authorities in the form of cash, letters of credit, performance bonds, asset liens or other arrangements agreeable with the tax authorities until the disputes are resolved. The Company expects that the ultimate outcome of these matters will not have a material impact on its results of operations or financial condition. However, the Company can provide no assurance as to the ultimate outcome of these matters, and the impact could be material if they are not resolved in the Company’s favor. As of September 30, 2017, the amount reserved related to these reassessments was immaterial to the Company’s consolidated financial statements. Additionally, the Company has other uncertain tax positions as well as assessments and disputed positions with taxing authorities in its various jurisdictions, which are consistent with those matters disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016.

Income Taxes:

The Company’s effective income tax rate differs from the U.S. statutory federal income tax rate primarily due to U.S. statutory depletion, state income taxes (net of federal tax benefit), foreign income tax rate differentials, foreign mining taxes, domestic manufacturing deductions, interest expense recognition differences for book and tax purposes and a partial release of valuation allowance in connection with the acquisition of Produquímica. The Company’s effective rate is impacted by permanent tax deductions which have a less favorable impact as pretax income increases.

During the nine months ended September 30, 2017, the Company determined it is more likely than not that a portion of its Brazilian deferred tax assets acquired in connection with the acquisition of Produquímica will be used to reduce taxable income. Based on current estimates of taxable income, the Company projects to release approximately $25 million of valuation allowances during the year ending December 31, 2017. For the nine months ended September 30, 2017, the Company included approximately $12 million of this valuation allowance release in the calculation of the estimated annual effective tax rate for the current fiscal year, and approximately $13 million as a discrete income tax benefit.

The Company had $52.0 million and $53.6 million as of September 30, 2017, and December 31, 2016, respectively, of gross foreign federal net operating loss (“NOL”) carryforwards that have no expiration date. In addition, the Company had $10.8 million and $7.5 million as of September 30, 2017, and December 31, 2016, respectively, of gross foreign federal NOL carryforwards which expire beginning in 2033 and $1.3 million and $0.9 million as of September 30, 2017, and December 31, 2016, respectively, of tax-effected state NOL carryforwards which expire beginning in 2033.

Canadian provincial tax authorities have challenged tax positions claimed by one of the Company’s Canadian subsidiaries and have issued tax reassessments for years 2002-2012. The reassessments are a result of ongoing audits and total $104.4 million, including interest through September 30, 2017. The Company disputes these reassessments and will continue to work with the appropriate authorities in Canada to resolve the dispute. Although the Company believes it has recorded an adequate reserve for this matter, there is a reasonable possibility that the ultimate resolution of this dispute, and any related disputes for other open tax years, may be materially higher or lower than the amounts the Company has reserved for such disputes. In connection with this dispute, local regulations require the Company to post security with the tax authority until the dispute is resolved. The Company has posted collateral in the form of a $63.6 million performance bond, has paid $35.2 million (most of which is recorded in other assets in its consolidated balance sheets) and the remaining balance of $5.6 million is expected to be addressed later this year, which is necessary to proceed with future appeals or litigation.

In addition, Canadian federal and provincial taxing authorities had reassessed the Company for years 2004-2006, which had been previously settled by agreement among the Company, the Canada Revenue Agency and the Internal Revenue Service of the United States. The Company sought to enforce the agreement, which provided the basis upon which the returns were previously filed and settled. In July 2016, a trial commenced in the Tax Court of Canada with respect to the Canadian federal tax issues for these matters, and in March 2017, the Tax Court of Canada ruled in favor of the Company. The decision of the Tax Court of Canada was not appealed by the Canada Revenue Agency. As a result, the Company believes that reassessed Canadian tax, penalties and interest for the Company for years 2004-2006 of approximately $94.7 million are effectively resolved. The Company is in the process of having certain posted collateral returned in connection with the resolution of the dispute.

The Company received Canadian income tax reassessments for years 2007-2008. The total amount of the reassessments, including penalties and interest through September 30, 2017, related to this matter is $37.2 million. The Company does not agree with these adjustments and is receiving assistance from the tax jurisdictions for relief from the impact of double taxation as available in the tax treaty between the U.S. and Canada. The Company has filed protective Notices of Objection and has posted collateral in the form of a $10.2 million performance bond and a $8.0 million bank letter guarantee, which is necessary to proceed with future appeals or litigation. Although the outcome of examinations by taxing authorities is uncertain, the Company believes it has adequately reserved for this matter.

The Company expects that it will be required by local regulations to provide security for additional interest on the above unresolved disputed amounts and for any future reassessments issued by these Canadian tax authorities in the form of cash, letters of credit, performance bonds, asset liens or other arrangements agreeable with the tax authorities until the disputes are resolved.

The Company expects that the ultimate outcome of these matters will not have a material impact on its results of operations or financial condition. However, the Company can provide no assurance as to the ultimate outcome of these matters, and the impact could be material if they are not resolved in the Company’s favor. As of September 30, 2017, the amount reserved related to these reassessments was immaterial to the Company’s consolidated financial statements.

Additionally, the Company has other uncertain tax positions as well as assessments and disputed positions with taxing authorities in its various jurisdictions, which are consistent with those matters disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016.