Summary of Significant Accounting Policies	6 Months Ended
Jun. 30, 2013
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies This Quarterly Report on Form 10-Q (this "Report") should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2012. Organization and Nature of Operations. Kaiser Aluminum Corporation (together with its subsidiaries, unless the context otherwise requires, the “Company”) specializes in the production of semi-fabricated specialty aluminum products, such as aluminum sheet and plate and extruded and drawn products, used primarily in aerospace/high strength, general engineering, automotive, and other industrial end market applications. The Company has one operating segment, Fabricated Products. See Note 12 for additional information regarding the Company’s reportable segment and its other business units. Principles of Consolidation and Basis of Presentation. The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries and are prepared in accordance with United States generally accepted accounting principles (“GAAP”) and the rules and regulations of the Securities and Exchange Commission (the “SEC”) applicable for interim periods and therefore, do not include all information and footnotes necessary for a fair presentation of financial position, results of operations, and cash flows. The results of operations for the Company’s interim periods are not necessarily indicative of the results of operations that may be achieved for the entire 2013 fiscal year. The financial information as of December 31, 2012 is derived from the Company’s audited consolidated financial statements and footnotes for the year ended December 31, 2012 included in the Company’s Annual Report on Form 10-K. Use of Estimates in the Preparation of Financial Statements. The preparation of financial statements in accordance with GAAP requires the use of estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities known to exist as of the date the financial statements are published, and the reported amounts of revenues and expenses during the reporting period. Uncertainties with respect to such estimates and assumptions are inherent in the preparation of the Company’s consolidated financial statements; accordingly, it is possible that the actual results could differ from these estimates and assumptions, which could have a material effect on the reported amounts of the Company’s consolidated financial position and results of operations. Inventories. Inventories are stated at the lower of cost or market value. Finished products, work-in-process and raw material inventories are stated on the last-in, first-out (“LIFO”) basis. The Company recorded net non-cash LIFO benefits of approximately $9.2 and $4.9 during the quarters ended June 30, 2013 and June 30, 2012, respectively. The Company recorded net non-cash LIFO benefits of approximately $12.9 and $7.8 during the six months ended June 30, 2013 and June 30, 2012, respectively. These amounts are primarily a result of changes in metal prices and changes in inventory volumes. The excess of current cost over the stated LIFO value of inventory at June 30, 2013 and December 31, 2012 was $11.6 and $24.5, respectively. Other inventories, principally operating supplies and repair and maintenance parts, are stated at average cost. Inventory costs consist of material, labor and manufacturing overhead, including depreciation. Abnormal costs, such as idle facility expenses, freight, handling costs and spoilage, are accounted for as current period charges. All of the Company’s inventories at June 30, 2013 and December 31, 2012 were included in the Fabricated Products segment (see Note 2 for the components of inventories). Property, Plant, and Equipment – Net. Property, plant and equipment is recorded at cost (see Note 2). Construction in progress is included within Property, plant, and equipment – net on the Consolidated Balance Sheets. Interest related to the construction of qualifying assets is capitalized as part of the construction costs. The aggregate amount of interest capitalized is limited to the interest expense incurred in the period. The amount of interest expense capitalized as construction in progress was $0.7 and $0.5 during the quarters ended June 30, 2013 and June 30, 2012, respectively. The amount of interest expense capitalized as construction in progress was $1.1 during both six months ended June 30, 2013 and June 30, 2012. Depreciation is computed using the straight-line method at rates based on the estimated useful lives of the various classes of assets. Capital lease assets and leasehold improvements are depreciated on a straight-line basis over the shorter of the estimated useful lives of the assets or the lease term. Depreciation expense is not included in Cost of products sold, excluding depreciation and amortization, but is included in Depreciation and amortization on the Statements of Consolidated Income. For the quarters ended June 30, 2013 and June 30, 2012, the Company recorded depreciation expense of $6.5 and $6.0, respectively, relating to the Company’s operating facilities in its Fabricated Products segment. For the six months ended June 30, 2013 and June 30, 2012, the Company recorded depreciation expense of $13.0 and $11.8, respectively, relating to the Company’s operating facilities in its Fabricated Products segment. An immaterial amount of depreciation expense was also recorded relating to the Company’s Corporate and Other business unit for all periods presented in this Report. New Accounting Pronouncements. Accounting Standards Update (“ASU”) No. 2013-01, Balance Sheet (Topic 210): Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities (“ASU 2013-01”), was issued in January 2013. ASU 2013-01 clarifies that ordinary trade receivables and receivables are not within the scope of ASU No. 2011-11, Balance Sheet (Topic 210): Disclosures about Offsetting Assets and Liabilities (“ASU 2011-11”). Specifically, ASU 2011-11 applies only to derivatives, repurchase agreements and reverse purchase agreements, and securities borrowing and securities lending transactions that are either offset in accordance with specific criteria contained in the Financial Accounting Standards Board Accounting Standards Codification or subject to a master netting arrangement or similar agreement. The adoption of ASU 2013-01 by the Company in the first quarter of 2013 did not have a material impact on the consolidated financial statements. ASU No. 2013-02, Comprehensive Income (Topic 220): Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income (“ASU 2013-02”), was issued in February 2013. This ASU does not change the current requirements for reporting net income or other comprehensive income in financial statements. However, ASU 2013-02 requires an entity to provide information about the amounts reclassified out of accumulated other comprehensive income by component. In addition, an entity is required to present, either on the face of the statement where net income is presented or in the notes, significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income if the amount reclassified is required under GAAP to be reclassified to net income in its entirety in the same reporting period. Amounts not required under GAAP to be reclassified in their entirety to net income are to be disclosed as provided by GAAP. The adoption of ASU 2013-02 by the Company in the first quarter of 2013 did not have a material impact on the consolidated financial statements.

Summary of Significant Accounting Policies

This Quarterly Report on Form 10-Q (this "Report") should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2012.

Organization and Nature of Operations. Kaiser Aluminum Corporation (together with its subsidiaries, unless the context otherwise requires, the “Company”) specializes in the production of semi-fabricated specialty aluminum products, such as aluminum sheet and plate and extruded and drawn products, used primarily in aerospace/high strength, general engineering, automotive, and other industrial end market applications. The Company has one operating segment, Fabricated Products. See Note 12 for additional information regarding the Company’s reportable segment and its other business units.

Principles of Consolidation and Basis of Presentation. The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries and are prepared in accordance with United States generally accepted accounting principles (“GAAP”) and the rules and regulations of the Securities and Exchange Commission (the “SEC”) applicable for interim periods and therefore, do not include all information and footnotes necessary for a fair presentation of financial position, results of operations, and cash flows. The results of operations for the Company’s interim periods are not necessarily indicative of the results of operations that may be achieved for the entire 2013 fiscal year. The financial information as of December 31, 2012 is derived from the Company’s audited consolidated financial statements and footnotes for the year ended December 31, 2012 included in the Company’s Annual Report on Form 10-K.

Use of Estimates in the Preparation of Financial Statements. The preparation of financial statements in accordance with GAAP requires the use of estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities known to exist as of the date the financial statements are published, and the reported amounts of revenues and expenses during the reporting period. Uncertainties with respect to such estimates and assumptions are inherent in the preparation of the Company’s consolidated financial statements; accordingly, it is possible that the actual results could differ from these estimates and assumptions, which could have a material effect on the reported amounts of the Company’s consolidated financial position and results of operations.

Inventories. Inventories are stated at the lower of cost or market value. Finished products, work-in-process and raw material inventories are stated on the last-in, first-out (“LIFO”) basis. The Company recorded net non-cash LIFO benefits of approximately $9.2 and $4.9 during the quarters ended June 30, 2013 and June 30, 2012, respectively. The Company recorded net non-cash LIFO benefits of approximately $12.9 and $7.8 during the six months ended June 30, 2013 and June 30, 2012, respectively. These amounts are primarily a result of changes in metal prices and changes in inventory volumes. The excess of current cost over the stated LIFO value of inventory at June 30, 2013 and December 31, 2012 was $11.6 and $24.5, respectively. Other inventories, principally operating supplies and repair and maintenance parts, are stated at average cost. Inventory costs consist of material, labor and manufacturing overhead, including depreciation. Abnormal costs, such as idle facility expenses, freight, handling costs and spoilage, are accounted for as current period charges. All of the Company’s inventories at June 30, 2013 and December 31, 2012 were included in the Fabricated Products segment (see Note 2 for the components of inventories).

Property, Plant, and Equipment – Net. Property, plant and equipment is recorded at cost (see Note 2). Construction in progress is included within Property, plant, and equipment – net on the Consolidated Balance Sheets. Interest related to the construction of qualifying assets is capitalized as part of the construction costs. The aggregate amount of interest capitalized is limited to the interest expense incurred in the period. The amount of interest expense capitalized as construction in progress was $0.7 and $0.5 during the quarters ended June 30, 2013 and June 30, 2012, respectively. The amount of interest expense capitalized as construction in progress was $1.1 during both six months ended June 30, 2013 and June 30, 2012.

Depreciation is computed using the straight-line method at rates based on the estimated useful lives of the various classes of assets. Capital lease assets and leasehold improvements are depreciated on a straight-line basis over the shorter of the estimated useful lives of the assets or the lease term. Depreciation expense is not included in Cost of products sold, excluding depreciation and amortization, but is included in Depreciation and amortization on the Statements of Consolidated Income. For the quarters ended June 30, 2013 and June 30, 2012, the Company recorded depreciation expense of $6.5 and $6.0, respectively, relating to the Company’s operating facilities in its Fabricated Products segment. For the six months ended June 30, 2013 and June 30, 2012, the Company recorded depreciation expense of $13.0 and $11.8, respectively, relating to the Company’s operating facilities in its Fabricated Products segment. An immaterial amount of depreciation expense was also recorded relating to the Company’s Corporate and Other business unit for all periods presented in this Report.

New Accounting Pronouncements.

Accounting Standards Update (“ASU”) No. 2013-01, Balance Sheet (Topic 210): Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities (“ASU 2013-01”), was issued in January 2013. ASU 2013-01 clarifies that ordinary trade receivables and receivables are not within the scope of ASU No. 2011-11, Balance Sheet (Topic 210): Disclosures about Offsetting Assets and Liabilities (“ASU 2011-11”). Specifically, ASU 2011-11 applies only to derivatives, repurchase agreements and reverse purchase agreements, and securities borrowing and securities lending transactions that are either offset in accordance with specific criteria contained in the Financial Accounting Standards Board Accounting Standards Codification or subject to a master netting arrangement or similar agreement. The adoption of ASU 2013-01 by the Company in the first quarter of 2013 did not have a material impact on the consolidated financial statements.

ASU No. 2013-02, Comprehensive Income (Topic 220): Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income (“ASU 2013-02”), was issued in February 2013. This ASU does not change the current requirements for reporting net income or other comprehensive income in financial statements. However, ASU 2013-02 requires an entity to provide information about the amounts reclassified out of accumulated other comprehensive income by component. In addition, an entity is required to present, either on the face of the statement where net income is presented or in the notes, significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income if the amount reclassified is required under GAAP to be reclassified to net income in its entirety in the same reporting period. Amounts not required under GAAP to be reclassified in their entirety to net income are to be disclosed as provided by GAAP. The adoption of ASU 2013-02 by the Company in the first quarter of 2013 did not have a material impact on the consolidated financial statements.