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Note 1 - Basis of Preparation of Financial Statements | 9 Months Ended
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Sep. 30, 2018
Notes to Financial Statements |
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] | Note 1. Basis of Preparation of Financial Statements In the opinion of management, the accompanying unaudited interim condensed consolidated financial statements and notes to the unaudited interim condensed consolidated financial statements contain all adjustments, consisting of normal recurring items and items which are nonrecurring, necessary to present fairly, in all material respects, the financial position of Hecla Mining Company and its consolidated subsidiaries (in this report, "Hecla" or "the Company" or “we” or “our” or “us” refers to Hecla Mining Company and our subsidiaries, unless the context requires otherwise). These unaudited interim condensed consolidated financial statements should be read in conjunction with our audited consolidated financial statements and related footnotes as set forth in our annual report filed on Form 10 -K for the year ended December 31, 2017, as it may be amended from time to time. The results of operations for the periods presented may not be indicative of those which may be expected for a full year. The unaudited interim condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission ("SEC"). Certain information and footnote disclosures normally included in audited financial statements prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) have been condensed or omitted pursuant to those rules and regulations, although we believe that the disclosures are adequate for the information not to be misleading. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the financial statements, the reported amounts of revenues and expenses during the reporting period, and the disclosures of contingent liabilities. Accordingly, ultimate results could differ materially from those estimates. On July 20, 2018, we completed the acquisition of Klondex Mines Ltd. ("Klondex"). The unaudited interim condensed consolidated financial statements included herein reflect our ownership of the assets previously held by Klondex as of the July 20, 2018 acquisition date. In the third quarter of 2018, we identified errors impacting amounts reported for accumulated depreciation, depletion and amortization ("DDA") and DDA expense for our Casa Berardi unit from June 1, 2013 through June 30, 2018. Certain amounts in the condensed consolidated financial statements and notes thereto for the prior period have been revised to correct these errors. See Note 2 for more information on the errors and revisions made to amounts reported for the prior period.

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- Definition The entire disclosure for the organization, consolidation and basis of presentation of financial statements disclosure, and significant accounting policies of the reporting entity. May be provided in more than one note to the financial statements, as long as users are provided with an understanding of (1) the significant judgments and assumptions made by an enterprise in determining whether it must consolidate a VIE and/or disclose information about its involvement with a VIE, (2) the nature of restrictions on a consolidated VIE's assets reported by an enterprise in its statement of financial position, including the carrying amounts of such assets, (3) the nature of, and changes in, the risks associated with an enterprise's involvement with the VIE, and (4) how an enterprise's involvement with the VIE affects the enterprise's financial position, financial performance, and cash flows. Describes procedure if disclosures are provided in more than one note to the financial statements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -URI http://asc.fasb.org/topic&trid=2122149 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -URI http://asc.fasb.org/topic&trid=2197479 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -URI http://asc.fasb.org/topic&trid=2122369 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -URI http://asc.fasb.org/topic&trid=2134479 + Details
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