Summary of Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2019
Accounting Policies [Abstract]
Principles of Consolidation and Basis of Presentation	Principles of Consolidation and Basis of Presentation. The accompanying unaudited consolidated financial statements include the accounts of our 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 ("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 our interim periods are not necessarily indicative of the results of operations that may be achieved for the entire 2019 fiscal year. The financial information as of December 31, 2018 is derived from our audited consolidated financial statements and footnotes included in our Annual Report on Form 10-K for the year ended December 31, 2018.
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 our 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 our consolidated financial position and results of operations.
Fair Value Measurements	Fair Value Measurements. We apply the fair value hierarchy established by GAAP for the recognition and measurement of certain financial assets and liabilities. An asset or liability's fair value classification within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement. In determining fair value, we utilize valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible and consider counterparty risk in our assessment of fair value. We also review the underlying inputs that are significant to the fair value measurement of financial instruments to determine if a transfer among hierarchy levels is appropriate. We historically have not had significant transfers into or out of each hierarchy level. Financial assets and liabilities that we measure at fair value each period include our derivative instruments, equity investments related to our deferred compensation plan and debt investment securities classified as available for sale securities (see Note 4). Additionally, we measure at fair value once each year at December 31 our Canadian defined benefit pension plan and the plan assets of the Salaried VEBA (defined in Note 4). We record our remaining financial assets and liabilities at carrying value. For a majority of our non-financial assets and liabilities, which include goodwill, intangible assets, inventories and property, plant and equipment, we are not required to measure their fair value on a recurring basis. However, if certain triggering events occur (or at least annually for goodwill), an evaluation of the affected non-financial asset or liability will be required, which could result in a reduction to the carrying amount of such asset or liability. None of our non-financial assets and liabilities subject to fair value assessments on a non-recurring basis required a material adjustment to the carrying amount of such assets and liabilities for the quarter ended March 31, 2019.
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. At March 31, 2019 and December 31, 2018, the current cost of our inventory exceeded its stated LIFO value by $17.2 million and $31.7 million, respectively. Other inventories are stated on the first-in, first-out basis and consist of operating supplies, which are materials and supplies to be consumed during the production process. 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 (see Note 2 for the components of inventories).
Replacement Parts	Replacement Parts. Replacement parts consist of preventative maintenance and capital spare parts, which are stated on the first-in, first-out basis. Replacement parts are recorded within Prepaid expenses and other current assets or Other assets depending on whether or not the expected utilization of the replacement parts is to occur within the current operating cycle.
Property, Plant and Equipment - Net	Property, Plant and Equipment, Net. Property, plant and equipment, net is recorded at cost and includes construction in progress (see Note 2). Interest related to the construction of qualifying assets is capitalized as part of the construction costs. The amount of interest expense capitalized as construction in progress was $0.5 million during each of the quarters ended March 31, 2019 and March 31, 2018, respectively. Depreciation is computed using the straight-line method at rates based on the estimated useful lives of the various classes of assets. Finance 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. We classify assets as held for sale only when an asset is being actively marketed and expected to sell within 12 months. Assets held for sale are initially measured at the lesser of the assets' carrying amount and the fair value less costs to sell.
Derivative Financial Instruments	Derivative Financial Instruments. Consistent with guidelines established by management and approved by our Board of Directors, we use derivative financial instruments to mitigate our exposure to changes in the market price of aluminum, alloying metals, energy, and, to a lesser extent, foreign currency exchange rates. We do not use derivative financial instruments for trading or other speculative purposes. Hedging transactions are executed centrally on behalf of all of our operations to minimize transaction costs, monitor consolidated net exposures and allow for increased responsiveness to changes in market factors. We reflect the fair value of all of our derivative instruments on our Consolidated Balance Sheets (see Note 5). The fair value of hedges settling within one year is included in Prepaid expenses and other current assets or Other accrued liabilities. The fair value of hedges settling beyond one year is included in Other assets or Long-term liabilities. Our aluminum and energy derivatives qualify for hedge (deferral) accounting and, as such, we designate such hedges as cash flow hedges. Forward swap contracts for zinc and copper ("Alloying Metals") used in our fabrication operations are also designated as cash flow hedges. Unrealized gains and losses associated with our cash flow hedges are deferred in Other comprehensive income, net of tax, and reclassified to Cost of products sold, excluding depreciation and amortization and other items ("COGS") when such hedges settle (see Note 5).
Self Insurance of Workers' Compensation and Employee Healthcare Liabilities	Self Insurance of Workers' Compensation and Employee Healthcare Liabilities. We self-insure the majority of the costs of workers' compensation benefits and employee healthcare benefits and rely on insurance coverage to protect us from large losses on individual claims. Workers' compensation liabilities are based on a combination of estimates for: (i) incurred-but-not-reported claims and (ii) the ultimate expense of incurred claims. Such estimates are based on judgment, using our historical claims data and information and analysis provided by actuarial and claims advisors, our insurance carriers and other professionals. Our undiscounted workers' compensation liabilities were estimated at $28.1 million and $27.6 million as of March 31, 2019 and December 31, 2018, respectively. However, we accounted for our workers' compensation accrued liabilities on a discounted basis (see Note 2), using a discount rate of 2.50% and 3.00% at March 31, 2019 and December 31, 2018, respectively. Accrued liabilities for employee healthcare benefits, which are estimates of unpaid incurred medical and prescription drug costs as provided by our healthcare administrators, were $3.4 million and $3.6 million as of March 31, 2019 and December 31, 2018, respectively.
Short-Term Incentive Plans (STI Plans)	Short-Term Incentive Plans ("STI Plans"). We have annual short-term incentive compensation plans for senior management and certain other employees payable at our election in cash, shares of common stock or a combination of cash and shares of common stock. Amounts earned under STI Plans are based on our adjusted earnings before interest, taxes, depreciation and amortization ("Adjusted EBITDA"), modified for certain safety, quality, delivery, cost and individual performance factors. The Adjusted EBITDA targets are determined based on the return on adjusted net assets. Most of our production facilities have similar programs for both hourly and salaried employees. As of March 31, 2019, we had a liability of $3.9 million recorded within Accrued salaries, wages and related expenses for estimated probable future payments relating to the three month performance period of our 2019 STI Plan.
Long-Term Incentive Programs (LTI Programs)	Long-Term Incentive Programs. Executive officers and other key employees of the Company, as well as non-employee directors of the Company, are eligible to participate in the Kaiser Aluminum Corporation 2016 Equity and Incentive Compensation Plan approved by stockholders on May 26, 2016 ("2016 Plan"). At March 31, 2019, 503,379 shares were available for awards under the 2016 Plan. We issue new shares of our common stock upon vesting under the 2016 Plan.
New Accounting Pronouncements	Adoption of New Accounting Pronouncements ASU No. 2016-02, Leases (Topic 842): Amendments to the Financial Accounting Standards Board Accounting Standards Codification ("ASU 2016-02"), was issued in February 2016 (with amendments issued in 2018) and requires lessees to recognize a right-of-use asset and a lease liability for virtually all of their leases (other than leases that meet the definition of a short-term lease). For income statement purposes, a dual model was retained, requiring leases to be classified as either operating or finance. Operating leases will result in straight-line expense (similar to operating leases under the previous guidance) while finance leases will result in a front-loaded expense pattern (similar to capital leases under the previous guidance). We adopted ASU 2016-02 and its subsequent amendments (together "ASC 842") during the quarter ended March 31, 2019 using the transition approach provided for under ASU No. 2018-11, Leases (Topic 842): Targeted Improvements, which allowed us to apply the new lease standard as of January 1, 2019, rather than the beginning of the earliest period presented. We elected the package of practical expedients, which permitted us to: (i) not reassess whether any of our contracts contained leases; (ii) carry forward the historical lease classification of our existing leases; and (iii) not reassess initial direct costs for our existing leases. We did not elect to apply the hindsight practical expedient when determining lease term and assessing impairment of right-of-use assets. Due to our adoption of ASC 842, we recorded an operating lease right-of-use asset of $29.0 million, a current operating lease liability of $4.1 million and a long-term operating lease liability of $27.4 million on our Consolidated Balance Sheets as of January 1, 2019. There was no cumulative-effect adjustment to Retained earnings required. The standard did not materially impact our consolidated net earnings and had no impact on cash flows. Comparative information in this Report has not been adjusted and continues to be reported under the previous lease accounting rules. See Note 3 for details of the significant changes and quantitative impacts of the changes, as well as other required disclosures related to our adoption of ASC 842. There were no material impacts on our consolidated financial statements resulting from our adoption in the quarter ended March 31, 2019 of: (i) ASU No. 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting and (ii) ASU No. 2018-08, Not-for-Profit Entities (Topic 958): Clarifying the Scope and the Accounting Guidance for Contributions Received and Contributions Made. Accounting Pronouncements Issued But Not Yet Adopted ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"), was issued in June 2016. Under ASU 2016-13, existing guidance on reporting credit losses for trade and other receivables and available for sale debt securities will be replaced with a new forward-looking "expected loss" model that generally will result in the earlier recognition of allowances for losses. We are currently in the process of evaluating the impact of adopting ASU 2016-13 in 2020, but do not expect it to have a material impact on our consolidated financial statements. ASU No. 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract ("ASU 2018-15"), was issued in August 2018. Under ASU 2018-15, requirements for capitalizing implementation costs incurred in a hosting arrangement (cloud computing) that is a service contract, are to be aligned with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. We are currently in the process of evaluating the impact of adopting ASU 2018-15 in 2020, but do not expect it to have a material impact on our consolidated financial statements.
Leases	We determine if an agreement is a lease at inception. We have operating and finance leases for equipment and real estate that primarily have fixed lease payments. Our leases have remaining lease terms of one year to 15 years, some of which may include options to extend the lease for up to 20 years, and some of which may include options to terminate the lease within one year. None of our options to extend or terminate are reasonably certain of being exercised, and are therefore not included in our determination of lease assets and liabilities. Short-term leases with an initial term of 12 months or less are not recorded in our Consolidated Balance Sheets. As most of our leases do not provide an implicit rate, we use information available at the lease commencement date in determining an incremental borrowing rate when calculating our operating lease assets and operating lease liabilities. In determining the inputs to the incremental borrowing rate calculation, we make judgments about the value of the leased asset, our credit rating and the lease term including the probability of our exercising options to extend or terminate the underlying lease. Additionally, we make judgments around contractual asset substitution rights in determining whether a contract contains a lease. We have lease agreements with lease and non-lease components, which are generally accounted for separately. These non-lease components include items such as common area maintenance, taxes and insurance for our real estate leases, as well as maintenance charges related to our equipment leases. We have applied the practical expedient within ASU 2016-02 to not separate lease and non-lease components to only our embedded supply system equipment leases and have therefore accounted for both lease and non-lease components in determining the lease assets and liabilities. Many of our equipment leases contain clauses that require us to return the equipment with certain functionality intact. We account for these costs as residual value guarantees when the guarantee becomes probable of being owed. Our lease agreements do not contain any material restrictive covenants.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2019

Principles of Consolidation and Basis of Presentation

Principles of Consolidation and Basis of Presentation. The accompanying unaudited consolidated financial statements include the accounts of our 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 ("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 our interim periods are not necessarily indicative of the results of operations that may be achieved for the entire 2019 fiscal year. The financial information as of December 31, 2018 is derived from our audited consolidated financial statements and footnotes included in our Annual Report on Form 10-K for the year ended December 31, 2018.

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 our 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 our consolidated financial position and results of operations.

Fair Value Measurements

Fair Value Measurements. We apply the fair value hierarchy established by GAAP for the recognition and measurement of certain financial assets and liabilities. An asset or liability's fair value classification within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement. In determining fair value, we utilize valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible and consider counterparty risk in our assessment of fair value. We also review the underlying inputs that are significant to the fair value measurement of financial instruments to determine if a transfer among hierarchy levels is appropriate. We historically have not had significant transfers into or out of each hierarchy level.

Financial assets and liabilities that we measure at fair value each period include our derivative instruments, equity investments related to our deferred compensation plan and debt investment securities classified as available for sale securities (see Note 4). Additionally, we measure at fair value once each year at December 31 our Canadian defined benefit pension plan and the plan assets of the Salaried VEBA (defined in Note 4). We record our remaining financial assets and liabilities at carrying value.

For a majority of our non-financial assets and liabilities, which include goodwill, intangible assets, inventories and property, plant and equipment, we are not required to measure their fair value on a recurring basis. However, if certain triggering events occur (or at least annually for goodwill), an evaluation of the affected non-financial asset or liability will be required, which could result in a reduction to the carrying amount of such asset or liability.

None of our non-financial assets and liabilities subject to fair value assessments on a non-recurring basis required a material adjustment to the carrying amount of such assets and liabilities for the quarter ended March 31, 2019.

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. At March 31, 2019 and December 31, 2018, the current cost of our inventory exceeded its stated LIFO value by $17.2 million and $31.7 million, respectively. Other inventories are stated on the first-in, first-out basis and consist of operating supplies, which are materials and supplies to be consumed during the production process. 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 (see Note 2 for the components of inventories).

Replacement Parts

Replacement Parts. Replacement parts consist of preventative maintenance and capital spare parts, which are stated on the first-in, first-out basis. Replacement parts are recorded within Prepaid expenses and other current assets or Other assets depending on whether or not the expected utilization of the replacement parts is to occur within the current operating cycle.

Property, Plant and Equipment - Net

Property, Plant and Equipment, Net. Property, plant and equipment, net is recorded at cost and includes construction in progress (see Note 2). Interest related to the construction of qualifying assets is capitalized as part of the construction costs. The amount of interest expense capitalized as construction in progress was $0.5 million during each of the quarters ended March 31, 2019 and March 31, 2018, respectively.

Depreciation is computed using the straight-line method at rates based on the estimated useful lives of the various classes of assets. Finance 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.

We classify assets as held for sale only when an asset is being actively marketed and expected to sell within 12 months. Assets held for sale are initially measured at the lesser of the assets' carrying amount and the fair value less costs to sell.

Derivative Financial Instruments

Derivative Financial Instruments. Consistent with guidelines established by management and approved by our Board of Directors, we use derivative financial instruments to mitigate our exposure to changes in the market price of aluminum, alloying metals, energy, and, to a lesser extent, foreign currency exchange rates. We do not use derivative financial instruments for trading or other speculative purposes. Hedging transactions are executed centrally on behalf of all of our operations to minimize transaction costs, monitor consolidated net exposures and allow for increased responsiveness to changes in market factors.

We reflect the fair value of all of our derivative instruments on our Consolidated Balance Sheets (see Note 5). The fair value of hedges settling within one year is included in Prepaid expenses and other current assets or Other accrued liabilities. The fair value of hedges settling beyond one year is included in Other assets or Long-term liabilities.

Our aluminum and energy derivatives qualify for hedge (deferral) accounting and, as such, we designate such hedges as cash flow hedges. Forward swap contracts for zinc and copper ("Alloying Metals") used in our fabrication operations are also designated as cash flow hedges. Unrealized gains and losses associated with our cash flow hedges are deferred in Other comprehensive income, net of tax, and reclassified to Cost of products sold, excluding depreciation and amortization and other items ("COGS") when such hedges settle (see Note 5).

Self Insurance of Workers' Compensation and Employee Healthcare Liabilities

Self Insurance of Workers' Compensation and Employee Healthcare Liabilities. We self-insure the majority of the costs of workers' compensation benefits and employee healthcare benefits and rely on insurance coverage to protect us from large losses on individual claims. Workers' compensation liabilities are based on a combination of estimates for: (i) incurred-but-not-reported claims and (ii) the ultimate expense of incurred claims. Such estimates are based on judgment, using our historical claims data and information and analysis provided by actuarial and claims advisors, our insurance carriers and other professionals. Our undiscounted workers' compensation liabilities were estimated at $28.1 million and $27.6 million as of March 31, 2019 and December 31, 2018, respectively. However, we accounted for our workers' compensation accrued liabilities on a discounted basis (see Note 2), using a discount rate of 2.50% and 3.00% at March 31, 2019 and December 31, 2018, respectively. Accrued liabilities for employee healthcare benefits, which are estimates of unpaid incurred medical and prescription drug costs as provided by our healthcare administrators, were $3.4 million and $3.6 million as of March 31, 2019 and December 31, 2018, respectively.

Short-Term Incentive Plans (STI Plans)

Short-Term Incentive Plans ("STI Plans"). We have annual short-term incentive compensation plans for senior management and certain other employees payable at our election in cash, shares of common stock or a combination of cash and shares of common stock. Amounts earned under STI Plans are based on our adjusted earnings before interest, taxes, depreciation and amortization ("Adjusted EBITDA"), modified for certain safety, quality, delivery, cost and individual performance factors. The Adjusted EBITDA targets are determined based on the return on adjusted net assets. Most of our production facilities have similar programs for both hourly and salaried employees. As of March 31, 2019, we had a liability of $3.9 million recorded within Accrued salaries, wages and related expenses for estimated probable future payments relating to the three month performance period of our 2019 STI Plan.

Long-Term Incentive Programs (LTI Programs)

Long-Term Incentive Programs. Executive officers and other key employees of the Company, as well as non-employee directors of the Company, are eligible to participate in the Kaiser Aluminum Corporation 2016 Equity and Incentive Compensation Plan approved by stockholders on May 26, 2016 ("2016 Plan"). At March 31, 2019, 503,379 shares were available for awards under the 2016 Plan. We issue new shares of our common stock upon vesting under the 2016 Plan.

New Accounting Pronouncements

Adoption of New Accounting Pronouncements

ASU No. 2016-02, Leases (Topic 842): Amendments to the Financial Accounting Standards Board Accounting Standards Codification ("ASU 2016-02"), was issued in February 2016 (with amendments issued in 2018) and requires lessees to recognize a right-of-use asset and a lease liability for virtually all of their leases (other than leases that meet the definition of a short-term lease). For income statement purposes, a dual model was retained, requiring leases to be classified as either operating or finance. Operating leases will result in straight-line expense (similar to operating leases under the previous guidance) while finance leases will result in a front-loaded expense pattern (similar to capital leases under the previous guidance). We adopted ASU 2016-02 and its subsequent amendments (together "ASC 842") during the quarter ended March 31, 2019 using the transition approach provided for under ASU No. 2018-11, Leases (Topic 842): Targeted Improvements, which allowed us to apply the new lease standard as of January 1, 2019, rather than the beginning of the earliest period presented. We elected the package of practical expedients, which permitted us to: (i) not reassess whether any of our contracts contained leases; (ii) carry forward the historical lease classification of our existing leases; and (iii) not reassess initial direct costs for our existing leases. We did not elect to apply the hindsight practical expedient when determining lease term and assessing impairment of right-of-use assets. Due to our adoption of ASC 842, we recorded an operating lease right-of-use asset of $29.0 million, a current operating lease liability of $4.1 million and a long-term operating lease liability of $27.4 million on our Consolidated Balance Sheets as of January 1, 2019. There was no cumulative-effect adjustment to Retained earnings required. The standard did not materially impact our consolidated net earnings and had no impact on cash flows. Comparative information in this Report has not been adjusted and continues to be reported under the previous lease accounting rules. See Note 3 for details of the significant changes and quantitative impacts of the changes, as well as other required disclosures related to our adoption of ASC 842.

There were no material impacts on our consolidated financial statements resulting from our adoption in the quarter ended March 31, 2019 of: (i) ASU No. 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting and (ii) ASU No. 2018-08, Not-for-Profit Entities (Topic 958): Clarifying the Scope and the Accounting Guidance for Contributions Received and Contributions Made.

Accounting Pronouncements Issued But Not Yet Adopted

ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"), was issued in June 2016. Under ASU 2016-13, existing guidance on reporting credit losses for trade and other receivables and available for sale debt securities will be replaced with a new forward-looking "expected loss" model that generally will result in the earlier recognition of allowances for losses. We are currently in the process of evaluating the impact of adopting ASU 2016-13 in 2020, but do not expect it to have a material impact on our consolidated financial statements.

ASU No. 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract ("ASU 2018-15"), was issued in August 2018. Under ASU 2018-15, requirements for capitalizing implementation costs incurred in a hosting arrangement (cloud computing) that is a service contract, are to be aligned with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. We are currently in the process of evaluating the impact of adopting ASU 2018-15 in 2020, but do not expect it to have a material impact on our consolidated financial statements.

Leases

We determine if an agreement is a lease at inception. We have operating and finance leases for equipment and real estate that primarily have fixed lease payments. Our leases have remaining lease terms of one year to 15 years, some of which may include options to extend the lease for up to 20 years, and some of which may include options to terminate the lease within one year. None of our options to extend or terminate are reasonably certain of being exercised, and are therefore not included in our determination of lease assets and liabilities. Short-term leases with an initial term of 12 months or less are not recorded in our Consolidated Balance Sheets.

As most of our leases do not provide an implicit rate, we use information available at the lease commencement date in determining an incremental borrowing rate when calculating our operating lease assets and operating lease liabilities. In determining the inputs to the incremental borrowing rate calculation, we make judgments about the value of the leased asset, our credit rating and the lease term including the probability of our exercising options to extend or terminate the underlying lease. Additionally, we make judgments around contractual asset substitution rights in determining whether a contract contains a lease.

We have lease agreements with lease and non-lease components, which are generally accounted for separately. These non-lease components include items such as common area maintenance, taxes and insurance for our real estate leases, as well as maintenance charges related to our equipment leases. We have applied the practical expedient within ASU 2016-02 to not separate lease and non-lease components to only our embedded supply system equipment leases and have therefore accounted for both lease and non-lease components in determining the lease assets and liabilities.

Many of our equipment leases contain clauses that require us to return the equipment with certain functionality intact. We account for these costs as residual value guarantees when the guarantee becomes probable of being owed. Our lease agreements do not contain any material restrictive covenants.