Debt issuance, percentage of principal amount

No definition available.

Name:	kalu_DebtIssuancePercentageOfPrincipalAmount
Namespace Prefix:	kalu_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of principal amount of debt redeemed.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Aggregate amount of interest expense on all borrowings.

+ References

+ Details

Name:	us-gaap_InterestExpenseBorrowings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of the cost of borrowed funds accounted for as interest expense for debt.

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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Aggregate amount of interest paid or due on all long-term debt.

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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow for a long-term debt where the holder has highest claim on the entity's asset in case of bankruptcy or liquidation during the period.

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Balance Type:	credit
Period Type:	duration

- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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Namespace Prefix:
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Balance Type:
Period Type:

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Debt and Credit Facility (6.50% Senior Notes) - Additional Information (Details) - Senior Notes Due 2025 - USD ($)		3 Months Ended
	May 21, 2021	Mar. 31, 2021	May 01, 2020	Apr. 28, 2020
Debt Instrument
Debt issuance, percentage of principal amount			101.00%	100.00%
Percentage of redemption price of principal amount	108.83%
Debt accrued and unpaid interest	$ 1,300,000
Debt aggregate principal amount			$ 50,000,000.0	$ 300,000,000.0
Unamortized debt issuance costs	5,000,000.0
Loss on extinguishment of debt	(35,900,000)
Premium payment	30,900,000
Repayments of Senior Debt	$ 382,200,000
Senior Notes
Debt Instrument
Debt instrument contractual rate (percent)		6.50%
Effective interest rate (percent)		6.80%
Interest expense		$ 6,000,000.0