Line of credit facility additional revolving commitments amount.

No definition available.

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Namespace Prefix:	kalu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Date the declared dividend will be paid, in YYYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-3

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of paid and unpaid cash, stock, and paid-in-kind (PIK) dividends declared, for example, but not limited to, common and preferred stock.

+ References

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+ Details

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

- Definition

Date the dividend to be paid was declared, in YYYY-MM-DD format.

+ References

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

- Definition

Date the holder must own the stock to be entitled to the dividend, in YYYY-MM-DD format.

+ References

No definition available.

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Description of the terms of a credit facility arrangement. Terms typically include interest rate, collateral required, guarantees required, repayment requirements, and restrictions on use of assets and activities of the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 830
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- Details

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- Details

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Subsequent Events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended						9 Months Ended
	Oct. 14, 2025	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Dec. 31, 2024	Apr. 30, 2022	Oct. 31, 2019
Subsequent Event [Line Items]
Cash dividends declared (in dollars per share)		$ 0.77	$ 0.77	$ 0.77	$ 0.77	$ 0.77	$ 0.77
Revolving Credit Facility
Subsequent Event [Line Items]
Line of credit mature description								The Revolving Credit Facility contains a maximum commitment amount of $575.0 million (of which up to a maximum of $50.0 million may be utilized for letters of credit) and, prior to the October 14, 2025 amendment, had a maturity date of April 2027.
Revolving Credit Facility borrowing commitment		$ 575.0						$ 575.0		$ 575.0
Outstanding borrowings		$ 0.0						$ 0.0	$ 0.0
Prime Rate \| Revolving Credit Facility
Subsequent Event [Line Items]
Effective interest rate (percent)											0.25%
SOFR \| Revolving Credit Facility \| Amended Credit Agreement
Subsequent Event [Line Items]
Effective interest rate (percent)											1.35%
Letter of Credit \| Revolving Credit Facility
Subsequent Event [Line Items]
Revolving Credit Facility borrowing commitment										$ 50.0
Subsequent Events \| O 2025 Q3 Dividends
Subsequent Event [Line Items]
Cash dividends declared (in dollars per share)	$ 0.77
Cash dividends declared	$ 12.8
Cash dividends, declared date	Oct. 14, 2025
Cash dividends, payable date	Nov. 14, 2025
Cash dividends, record date	Oct. 24, 2025
Subsequent Events \| Revolving Credit Facility \| Amended Credit Agreement
Subsequent Event [Line Items]
Line of credit mature description	The Amended Credit Facility, among other things, (i) contains a maximum commitment amount of $575.0 million (of which up to a maximum of $50.0 million may be utilized for letters of credit), (ii) allows the Company to request an increase of the revolving commitments by up to an amount equal to $200.0 million plus an additional amount for a first-in last-out tranche, subject to certain conditions and the agreement of one or more lenders to provide such increased commitment
Revolving Credit Facility borrowing commitment	$ 575.0
Line of credit facility additional revolving commitments amount	200.0
Subsequent Events \| Letter of Credit \| Revolving Credit Facility \| Amended Credit Agreement
Subsequent Event [Line Items]
Revolving Credit Facility borrowing commitment	50.0
Outstanding borrowings	$ 14.6
Subsequent Events \| Maximum \| Base Rate \| Revolving Credit Facility \| Amended Credit Agreement
Subsequent Event [Line Items]
Effective interest rate (percent)	0.50%
Subsequent Events \| Maximum \| SOFR \| Revolving Credit Facility \| Amended Credit Agreement
Subsequent Event [Line Items]
Effective interest rate (percent)	1.50%
Subsequent Events \| Minimum \| Base Rate \| Revolving Credit Facility \| Amended Credit Agreement
Subsequent Event [Line Items]
Effective interest rate (percent)	0.25%
Subsequent Events \| Minimum \| SOFR \| Revolving Credit Facility \| Amended Credit Agreement
Subsequent Event [Line Items]
Effective interest rate (percent)	1.25%