Summary of Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2014
Accounting Policies [Abstract]
Organization and Nature of Operations	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, primarily used in aerospace/high strength, general engineering, automotive, and other industrial end market applications. The Company has one operating segment, Fabricated Products. See Note 11 for additional information regarding the Company’s reportable segment and its other business units.
Principles of Consolidation and Basis of Presentation	Principles of Consolidation and Basis of Presentation. The accompanying unaudited 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 required by GAAP for complete financial statements. In management’s opinion, all adjustments (which include normal recurring adjustments) considered necessary for a fair presentation have been included. 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 2014 fiscal year. The financial information as of December 31, 2013 is derived from the Company’s audited consolidated financial statements and footnotes for the year ended December 31, 2013 included in the Company’s Annual Report on Form 10-K.
Use of Estimates in the Preparation of Financial Statements	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. 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. During the quarter ended March 31, 2014, the Company decremented a prior year, higher cost LIFO layer which resulted in a $1.8 charge. The excess of current cost over the stated LIFO value of inventory at March 31, 2014 and December 31, 2013 was $11.1 and $0.4, 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 March 31, 2014 and December 31, 2013 were included in the Fabricated Products segment (see Note 2 for the components of inventories).
Property, Plant and Equipment - Net	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 $1.1 and $0.4 during the quarters ended March 31, 2014 and March 31, 2013, respectively. 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 March 31, 2014 and March 31, 2013, the Company recorded depreciation expense of $6.8 and $6.5, 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	New Accounting Pronouncements. ASU No. 2013-11, Income Taxes (Topic 740): Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. (“ASU 2013-11”), was issued in July 2013. ASU 2013-11 requires an entity to present in the financial statements an unrecognized tax benefit, or a portion of an unrecognized tax benefit, as a reduction to a deferred tax asset resulting from a net operating loss carryforward, a similar tax loss, or a tax credit carryforward. However, when the above situation is not available at the reporting date or the tax law of the applicable jurisdiction does not require the entity to use the deferred tax asset for such purpose, the unrecognized tax benefit should be presented in the financial statements as a liability and should not be combined with deferred tax assets. An entity is required to adopt ASU 2013-11 for annual and interim periods beginning after December 15, 2013. The Company’s adoption of ASU 2013-11 in the first quarter of 2014 did not have a material impact on its financial statements.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2014

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, primarily used in aerospace/high strength, general engineering, automotive, and other industrial end market applications. The Company has one operating segment, Fabricated Products. See Note 11 for additional information regarding the Company’s reportable segment and its other business units.

Principles of Consolidation and Basis of Presentation

Principles of Consolidation and Basis of Presentation. The accompanying unaudited 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 required by GAAP for complete financial statements. In management’s opinion, all adjustments (which include normal recurring adjustments) considered necessary for a fair presentation have been included. 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 2014 fiscal year. The financial information as of December 31, 2013 is derived from the Company’s audited consolidated financial statements and footnotes for the year ended December 31, 2013 included in the Company’s Annual Report on Form 10-K.

Use of Estimates in the Preparation of Financial Statements

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. 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. During the quarter ended March 31, 2014, the Company decremented a prior year, higher cost LIFO layer which resulted in a $1.8 charge. The excess of current cost over the stated LIFO value of inventory at March 31, 2014 and December 31, 2013 was $11.1 and $0.4, 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 March 31, 2014 and December 31, 2013 were included in the Fabricated Products segment (see Note 2 for the components of inventories).

Property, Plant and Equipment - Net

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 $1.1 and $0.4 during the quarters ended March 31, 2014 and March 31, 2013, respectively.

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 March 31, 2014 and March 31, 2013, the Company recorded depreciation expense of $6.8 and $6.5, 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

New Accounting Pronouncements.

ASU No. 2013-11, Income Taxes (Topic 740): Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. (“ASU 2013-11”), was issued in July 2013. ASU 2013-11 requires an entity to present in the financial statements an unrecognized tax benefit, or a portion of an unrecognized tax benefit, as a reduction to a deferred tax asset resulting from a net operating loss carryforward, a similar tax loss, or a tax credit carryforward. However, when the above situation is not available at the reporting date or the tax law of the applicable jurisdiction does not require the entity to use the deferred tax asset for such purpose, the unrecognized tax benefit should be presented in the financial statements as a liability and should not be combined with deferred tax assets. An entity is required to adopt ASU 2013-11 for annual and interim periods beginning after December 15, 2013. The Company’s adoption of ASU 2013-11 in the first quarter of 2014 did not have a material impact on its financial statements.

- Definition

Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02, 03

-Article 3A

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367646&loc=d3e18780-107790

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-URI http://asc.fasb.org/subtopic&trid=2197480

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 40

-Section 45

-URI http://asc.fasb.org/section&trid=2197723

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-URI http://asc.fasb.org/subtopic&trid=2196966

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 325

-SubTopic 20

-URI http://asc.fasb.org/subtopic&trid=2197087

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.3A-02)

-URI http://asc.fasb.org/extlink&oid=27015204&loc=d3e355033-122828

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33801-111570

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=18733093&loc=d3e5614-111684

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph k

-Article 1

+ Details

- Definition

Disclosure of accounting policy for major classes of inventories, bases of stating inventories (for example, lower of cost or market), methods by which amounts are added and removed from inventory classes (for example, FIFO, LIFO, or average cost), loss recognition on impairment of inventories, and situations in which inventories are stated above cost. If inventory is carried at cost, this disclosure includes the nature of the cost elements included in inventory.

+ References+ Details

- Definition

Disclosure of accounting policy for long-lived, physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, basis of assets, depreciation and depletion methods used, including composite deprecation, estimated useful lives, capitalization policy, accounting treatment for costs incurred for repairs and maintenance, capitalized interest and the method it is calculated, disposals and impairments.

+ References+ Details