COMPASS MINERALS INTERNATIONAL INC, 10-Q filed on 2/6/2026
Quarterly Report
v3.25.4
Cover Page - shares
 3 Months Ended
Dec. 31, 2025
Jan. 30, 2026
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Dec. 31, 2025  
Document Transition Report false  
Entity File Number 001-31921  
Entity Registrant Name Compass Minerals International, Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 36-3972986  
Entity Address, Address Line One 9900 West 109th Street  
Entity Address, Address Line Two Suite 100  
Entity Address, City or Town Overland Park  
Entity Address, State or Province KS  
Entity Address, Postal Zip Code 66210  
City Area Code 913  
Local Phone Number 344-9200  
Title of 12(b) Security Common stock, $0.01 par value  
Trading Symbol CMP  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   41,863,273
Entity Central Index Key 0001227654  
Current Fiscal Year End Date --09-30  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q1  
Amendment Flag false  
v3.25.4
CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Millions
Dec. 31, 2025
Sep. 30, 2025
Assets, Current [Abstract]    
Cash and cash equivalents $ 46.7 $ 59.7
Receivables, less allowance for credit losses and rebates of $3.4 and $2.2 at December 31, 2025 and September 30, 2025, respectively 278.6 179.6
Inventories, less allowance of $6.6 and $7.7 at December 31, 2025 and September 30, 2025, respectively 258.4 312.0
Other current assets 48.5 20.9
Total current assets 632.2 572.2
Property, plant and equipment, net 766.2 770.1
Intangible assets, net 23.7 23.8
Goodwill 6.0 6.0
Other noncurrent assets 98.6 147.3
Total assets 1,526.7 1,519.4
Current liabilities:    
Accounts payable 100.6 96.0
Accrued salaries and wages 16.6 26.4
Current portion of finance lease liabilities 6.9 7.9
Income taxes payable 0.0 5.6
Accrued interest 1.6 19.0
Accrued expenses and other current liabilities 118.0 110.7
Total current liabilities 243.7 265.6
Long-term debt, net of current portion 883.6 832.2
Finance lease liabilities, net of current portion 6.4 7.6
Deferred income taxes, net 59.1 53.9
Other noncurrent liabilities 73.4 126.0
Commitments and contingencies (Note 7)
Stockholders’ equity:    
Common stock: $0.01 par value, 200,000,000 authorized shares; 42,197,964 issued shares at December 31, 2025 and September 30, 2025 0.4 0.4
Additional paid-in capital 431.9 430.0
Treasury stock, at cost — 371,828 shares at December 31, 2025 and 497,420 shares at September 30, 2025 (11.6) (10.8)
Accumulated deficit (59.0) (77.6)
Accumulated other comprehensive loss (101.2) (107.9)
Total stockholders’ equity 260.5 234.1
Total liabilities and stockholders’ equity $ 1,526.7 $ 1,519.4
v3.25.4
CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)
$ in Millions
Dec. 31, 2025
Sep. 30, 2025
ASSETS    
Allowance for doubtful accounts $ 3.4 $ 2.2
Inventory allowance $ 6.6 $ 7.7
Stockholders’ equity:    
Common stock, par or stated value per share (in dollars per share) $ 0.01 $ 0.01
Common stock, shares authorized (in shares) 200,000,000 200,000,000
Common stock, shares issued (in shares) 42,197,964 42,197,964
Treasury stock, shares (in shares) 371,828 497,420
v3.25.4
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)
shares in Thousands, $ in Millions
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Sales $ 396.1 $ 307.2
Gross profit 63.2 34.3
Selling, general and administrative expenses 26.6 33.3
Other operating expense 0.0 0.5
Operating income 36.6 0.5
Other expense (income):    
Interest income (0.3) (0.4)
Interest expense 18.1 16.9
Loss (gain) on foreign exchange 2.1 (5.2)
Other expense, net 0.3 3.1
Net income (loss) before income taxes 16.4 (13.9)
Income tax (benefit) expense (2.2) 9.7
Net income (loss) $ 18.6 $ (23.6)
Basic net income (loss) per common share (in dollars per share) $ 0.43 $ (0.57)
Diluted net income (loss) per common share (in dollars per share) $ 0.43 $ (0.57)
Weighted-average common shares outstanding (in thousands):    
Basic (in shares) 42,083 41,441
Diluted (in shares) 42,267 41,441
Shipping and handling cost    
Cost $ 112.1 $ 80.6
Product cost    
Cost $ 220.8 $ 192.3
v3.25.4
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($)
$ in Millions
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Statement of Comprehensive Income [Abstract]    
Net income (loss) $ 18.6 $ (23.6)
Other comprehensive income (loss):    
Unrealized gain from change in pension obligations, net of tax of $(0.1) for both the three months ended December 31, 2025 and December 31, 2024 0.2 0.2
Unrealized loss from change in other postretirement benefits, net of tax of $0.0 for both the three months ended December 31, 2025 and December 31, 2024 0.0 (0.1)
Unrealized loss on cash flow hedges, net of tax of $0.0 for both the three months ended December 31, 2025 and December 31, 2024 (0.5) (0.3)
Unrealized foreign currency translation adjustments 7.0 (33.3)
Other comprehensive income (loss) 6.7 (33.5)
Total comprehensive income (loss) $ 25.3 $ (57.1)
v3.25.4
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($)
$ in Millions
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Statement of Comprehensive Income [Abstract]    
Unrealized gain (loss) from change in pension obligations, tax $ (0.1) $ (0.1)
Unrealized loss, other postretirement benefits, tax 0.0 0.0
Unrealized income (loss) on cash flow hedges, tax $ 0.0 $ 0.0
v3.25.4
CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($)
$ in Millions
Total
Common Stock
Additional Paid-In Capital
Treasury Stock
Retained Earnings (Loss)
Accumulated Other Comprehensive Loss
Beginning Balance at Sep. 30, 2024 $ 316.6 $ 0.4 $ 420.6 $ (10.2) $ 2.2 $ (96.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Total comprehensive income (57.1)       (23.6) (33.5)
Shares issued for stock units, net of shares withheld for taxes (0.4)   (0.2) (0.2)    
Stock-based compensation 3.9   3.9      
Ending Balance at Dec. 31, 2024 263.0 0.4 424.3 (10.4) (21.4) (129.9)
Beginning Balance at Sep. 30, 2025 234.1 0.4 430.0 (10.8) (77.6) (107.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Total comprehensive income 25.3       18.6 6.7
Shares issued for stock units, net of shares withheld for taxes (1.2)   (0.4) (0.8)    
Stock-based compensation 2.3   2.3      
Ending Balance at Dec. 31, 2025 $ 260.5 $ 0.4 $ 431.9 $ (11.6) $ (59.0) $ (101.2)
v3.25.4
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)
$ in Millions
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Cash flows from operating activities:    
Net income (loss) $ 18.6 $ (23.6)
Adjustments to reconcile net income (loss) to net cash flows provided by operating activities:    
Depreciation, depletion and amortization 26.4 26.8
Amortization of deferred financing costs 1.0 0.8
Non-cash portion of stock-based compensation 2.3 3.9
Deferred income taxes 4.5 2.7
Unrealized foreign exchange loss (gain) 2.1 (5.7)
Other, net 1.7 (0.9)
Changes in operating assets and liabilities:    
Receivables (98.8) (61.3)
Inventories 51.7 39.1
Other assets 21.6 (2.0)
Accounts payable and accrued expenses and other current liabilities (13.6) 9.1
Other liabilities (54.5) 7.0
Net cash used in operating activities (37.0) (4.1)
Cash flows from investing activities:    
Capital expenditures (22.8) (21.8)
Other, net (0.5) (0.4)
Net cash used in investing activities (23.3) (22.2)
Cash flows from financing activities:    
Borrowings under revolving credit facility 47.0 140.3
Repayments under revolving credit facility (37.0) (100.8)
Proceeds from issuance of long-term debt 42.8 19.6
Principal payments on long-term debt (2.1) (1.6)
Payment of deferred financing costs 0.0 (2.4)
Shares withheld to satisfy employee tax obligations (1.2) (0.4)
Other, net (2.4) (1.6)
Net cash provided by financing activities 47.1 53.1
Effect of exchange rate changes on cash and cash equivalents 0.2 (1.2)
Net change in cash and cash equivalents (13.0) 25.6
Cash and cash equivalents, beginning of the year 59.7 20.2
Cash and cash equivalents, end of period 46.7 45.8
Supplemental cash flow information:    
Interest paid, net of amounts capitalized 34.4 23.4
Income taxes paid, net of refunds 28.7 8.0
Non-cash activities:    
Right-of-use assets obtained in exchange for new operating lease liabilities 1.9 6.8
Right-of use assets obtained in exchange for new finance lease liabilities $ 0.0 $ 6.0
v3.25.4
ACCOUNTING POLICIES AND BASIS OF PRESENTATION
 3 Months Ended
Dec. 31, 2025
Accounting Policies [Abstract]  
ACCOUNTING POLICIES AND BASIS OF PRESENTATION ACCOUNTING POLICIES AND BASIS OF PRESENTATION
Compass Minerals International, Inc. (“CMI”), through its subsidiaries (collectively, the “Company”), is a leading global provider of essential minerals focused on safely delivering where and when it matters to help solve nature’s challenges for customers and communities. The Company’s salt products help keep roadways safe during winter weather and are used in numerous other consumer, industrial, chemical and agricultural applications. Its plant nutrition business is the leading North American producer of sulfate of potash (“SOP”), which is used in the production of specialty fertilizers for high-value crops and turf and helps improve the quality and yield of crops, while supporting sustainable agriculture. The Company’s principal products are salt, consisting of sodium chloride and magnesium chloride, and SOP. The Company’s production sites are located in the United States (“U.S.”), Canada and the United Kingdom (“U.K.”). The Company also provides records management services in the U.K. Except where otherwise noted, references to North America include only the continental U.S. and Canada, and references to the U.K. include only England, Scotland and Wales. References to “Compass Minerals,” “our,” “us” and “we” refer to CMI and its consolidated subsidiaries.
 
CMI is a holding company with no significant operations other than those of its wholly-owned subsidiaries. The consolidated financial statements include the accounts of CMI and its wholly-owned domestic and foreign subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.

The accompanying condensed consolidated balance sheet as of September 30, 2025, which was derived from audited financial statements, and the unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete consolidated financial statements. As a result, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2025 (“2025-K”). In the opinion of management, these interim financial statements reflect all adjustments, consisting of normal recurring adjustments considered necessary for a fair presentation of the Company’s financial position and results of operations.
 
Accounting Pronouncements Issued Not Yet Adopted

Income Tax Disclosures. In December 2023, the Financial Accounting Standards Board (“FASB”) issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which updates income tax disclosures by requiring consistent categories and additional disaggregation of information in the rate reconciliation and income taxes paid by jurisdiction. The ASU is effective for fiscal years beginning after December 15, 2024, and is effective for the Company beginning in the annual report for the fiscal year ended September 30, 2026. Early adoption is permitted. The amendments should be applied prospectively; however, retrospective application is permitted. Management is currently evaluating this ASU to determine its impact on the Company’s disclosures.

Disaggregation of Income Statement Expenses. In November 2024, the FASB issued amended guidance related to disclosure of disaggregated expenses (“ASU 2024-03”). This amendment requires public business entities to provide detailed disclosures in the notes to financial statements disaggregating specific expense categories, including employee compensation, depreciation, and intangible asset amortization, as well as certain other disclosures to provide enhanced transparency into the nature and function of expenses. This guidance is effective for annual periods beginning in the Company’s annual report for the fiscal year ended September 30, 2028 and interim periods following annual adoption, with early adoption permitted. This guidance will be applied on a prospective basis with retrospective application permitted. Management is currently evaluating ASU 2024-03 to determine its impact on the Company’s disclosures.

Interim Reporting. In December 2025, the FASB issued ASU 2025-11, Interim Reporting (Topic 270): Narrow-Scope Improvements (“ASU 2025-11”), to improve the guidance for interim reporting and clarify when that guidance is applicable. This ASU provides a comprehensive list of required interim disclosures and also requires entities to disclose events since the end of the last annual reporting period that have a material impact on the entity. ASU 2025-11 is effective for interim reporting periods within annual reporting periods beginning after December 15, 2027. For the Company, the guidance becomes effective in the first interim period of the fiscal year ended September 30, 2029. Early adoption is permitted. Management is currently evaluating ASU 2025-11 to determine its impact on the Company’s disclosures.
v3.25.4
REVENUES
 3 Months Ended
Dec. 31, 2025
Revenue from Contract with Customer [Abstract]  
REVENUES REVENUES
Disaggregation of Revenue

Revenue is disaggregated in the following table by timing of revenue recognition (in millions):
 Three Months Ended
December 31,
 20252024
Timing of revenue recognition:
Products and services transferred at a point in time$393.3 $304.6 
Products and services transferred over time(a)
2.8 2.6 
Total revenues$396.1 $307.2 
(a)     Amounts include records management business utilizing excavated areas of its Winsford salt mine with one other location in London, England.

For disaggregation of sales by segment and type, see Note 8. Operating Segments.

Receivables

The following table provides the balances of receivables (in millions):
 December 31,
2025		September 30,
2025
Current Assets:
Receivables related to contracts with customers
$226.4 $127.3 
Miscellaneous receivables(a)
52.2 52.3 
Total receivables
$278.6 $179.6 
(a)Refer to Note 7. Commitments and Contingencies for additional information.

Deferred Revenue

Deferred revenue represents collections under non-cancellable contracts before the related product or service is transferred to the customer. The portion of deferred revenue that is anticipated to be recognized as revenue during the succeeding twelve-month period is recorded in accrued expenses and other current liabilities on the Consolidated Balance Sheets. Deferred revenue included in Accrued expenses and other current liabilities as of both December 31, 2025 and September 30, 2025 was approximately $1.6 million. Of the total deferred revenues in the Condensed Consolidated Balance Sheet as of September 30, 2025 that were reclassified to revenue as the result of performance obligations being satisfied during the three months ended December 31, 2025 was de minimis.
v3.25.4
INVENTORIES
 3 Months Ended
Dec. 31, 2025
Inventory Disclosure [Abstract]  
INVENTORIES INVENTORIES
 
Inventories consist of the following (in millions):
 December 31,
2025		September 30,
2025
Finished goods$162.5 $219.1 
Work in process5.9 5.9 
Raw materials and supplies(a)
90.0 87.0 
Total inventories$258.4 $312.0 
(a)Excludes certain raw materials and supplies of $33.2 million and $33.0 million as of December 31, 2025 and September 30, 2025, respectively, that are not expected to be consumed within the next twelve months, included in Other noncurrent assets in the Condensed Consolidated Balance Sheets.
v3.25.4
PROPERTY, PLANT AND EQUIPMENT, NET
 3 Months Ended
Dec. 31, 2025
Property, Plant and Equipment [Abstract]  
PROPERTY, PLANT AND EQUIPMENT, NET PROPERTY, PLANT AND EQUIPMENT, NET
 
Property, plant and equipment, net, consists of the following (in millions):
 December 31,
2025		September 30,
2025
Land, buildings and structures, and leasehold improvements$559.1 $554.1 
Machinery and equipment1,171.9 1,154.9 
Office furniture and equipment24.0 23.9 
Mineral interests169.8 169.1 
Construction in progress53.5 51.6 
 1,978.3 1,953.6 
Less: accumulated depreciation and depletion(1,212.1)(1,183.5)
Property, plant and equipment, net$766.2 $770.1 

The following table provides supplemental non-cash activities (in million):
Three Months Ended
December 31,
 20252024
Purchases of Property, plant and equipment in Accounts payable$5.5 $2.7 
Purchases of Property, plant and equipment in Accrued expenses and other current liabilities4.4 4.0 
Transfers of Property, plant and equipment from Inventory3.1 0.4 
v3.25.4
INCOME TAXES
 3 Months Ended
Dec. 31, 2025
Income Tax Disclosure [Abstract]  
INCOME TAXES INCOME TAXES
The Company’s effective income tax rate differs from the U.S. statutory federal income tax rate primarily due to U.S. statutory depletion, state income taxes (net of federal tax benefit), nondeductible executive compensation over $1 million, foreign income, mining and withholding taxes, base erosion and anti-abuse tax, and valuation allowances recorded on deferred tax assets.

The effective tax rates applied to the three months ended December 31, 2025 were determined by excluding the U.S. losses from the overall estimated annual effective tax rate computations and a separate estimated annual effective tax rate was computed and applied to the ordinary U.S. losses.

Management assesses the available positive and negative evidence to estimate whether sufficient future taxable income will be generated to permit use of the existing deferred tax assets. A significant piece of objective negative evidence evaluated was the cumulative loss incurred in the U.S. over the three-year period ended December 31, 2025. Such objective evidence limits the ability to consider other subjective evidence, such as the Company’s projections for future income. On the basis of this evaluation, during the three months ended December 31, 2025, no change in valuation allowance has been recorded to recognize the portion of the U.S. deferred tax assets that is more likely than not to be realized. The amount of the deferred tax assets considered realizable, however, could be adjusted if objective negative evidence in the form of cumulative losses is no longer present and additional weight is given to subjective evidence such as the Company’s projections for income.

As of both December 31, 2025 and September 30, 2025, the Company had $80.5 million of gross federal NOL carryforwards that have no expiration date and $7.1 million at both December 31, 2025 and September 30, 2025 of net operating tax-effected state NOL carryforwards which expire beginning in 2031.

In November 2025, the Company reached a settlement with a Canadian provincial tax authority regarding a tax dispute for fiscal years 2002 through 2018. The Canadian provincial tax authority had challenged tax positions claimed by one of the Company’s Canadian subsidiaries and issued tax reassessments for fiscal years 2002 through 2020. The reassessments were the result of ongoing audits and totaled $209.8 million, including interest as of September 30, 2025.
The settlement resolved the dispute for tax years 2002 through 2018. In connection with the settlement, the Company has also revised its mining tax calculations for tax years subsequent to 2018 consistent with the principles agreed to in the settlement agreement. The Company is in the process of amending the relevant tax returns to obtain the associated federal and provincial refunds. The total net expected cash outlay, after taking into account expected federal refunds and deductions associated with the agreed upon tax and interest as well as estimated subsequent tax year impacts is $8.2 million. Additionally, the settlement and other updates to uncertain tax positions resulted in an overall tax benefit of $6.2 million, for the three months ended December 31, 2025.

The Company previously paid $35.8 million over a period of several years to the Canadian tax authorities as a deposit, which was recorded in Other noncurrent assets in the Consolidated Balance Sheets. The deposit was previously required to be paid by the Company to proceed with future appeals or litigation and was subsequently applied to the amount due at settlement. The remaining settlement amount of $24.8 million related to tax years 2002 through 2018 was paid during the three months ended December 31, 2025.

The additional impacts of the settlement on the Consolidated Balance Sheets at December 31, 2025, as compared to September 30, 2025, included an increase of $21.9 million in Other current assets, due to expected federal refunds from amended returns to be filed; a decrease in Other noncurrent assets of $47.1 million, primarily due to the application of the deposit to the amount of the total settlement; and a decrease in Other noncurrent liabilities of $56.2 million, due to the change in reserves for uncertain tax positions. With the settlement, the performance bonds of $157.4 million posted as collateral for the 2002 through 2018 period were released.

On July 4, 2025, the U.S. enacted a budget reconciliation package known as the “One Big Beautiful Bill Act of 2025” (“OBBBA”), which includes both tax and non-tax provisions. While the Company will realize some benefit from the relaxing of interest deduction limitations, the Company does not view the legislation to significantly impact its income tax profile.
v3.25.4
LONG-TERM DEBT AND FINANCE LEASE LIABILITIES
 3 Months Ended
Dec. 31, 2025
Debt Disclosure [Abstract]  
LONG-TERM DEBT AND FINANCE LEASE LIABILITIES LONG-TERM DEBT AND FINANCE LEASE LIABILITIES
 
Total long-term carrying value of debt and finance lease liabilities consists of the following (in millions):
 December 31,
2025		September 30,
2025
Secured Debt:
Revolving Credit Facility due May 2028$10.0 $— 
Subordinated Debt:
8.00% Senior Notes due July 2030
650.0 650.0 
6.75% Senior Notes due December 2027
150.0 150.0 
Accounts Receivable Securitization Facility expires March 202786.5 45.8 
Total principal amount of debt896.5 845.8 
Finance lease liabilities13.3 15.5 
Unamortized deferred financing costs(12.9)(13.6)
Total carrying value of debt and finance lease liabilities896.9 847.7 
Current portion of finance lease liabilities(6.9)(7.9)
Total long-term carrying value of debt and finance lease liabilities$890.0 $839.8 

8.00% Senior Notes due 2030

On June 16, 2025, the Company issued $650.0 million aggregate principal amount of its 8.00% Senior Notes due 2030 in a private offering, pursuant to an indenture, dated June 16, 2025 (the “2030 Notes”), among the Company, the subsidiary guarantors named therein and Computershare Trust Company, N.A., as trustee. The 2030 Notes are senior unsecured obligations, with interest payable semi-annually on January 1 and July 1. The 2030 Notes are guaranteed by certain of the Company’s domestic subsidiaries. The 2030 Notes will mature on July 1, 2030. The Company incurred $13.0 million in deferred financing costs, including arrangement, legal and other fees, and will be amortized to interest expense over the 5-year term of the 2030 Notes.
The indenture governing the 2030 Notes contains covenants limiting other indebtedness, dividends, purchases or redemptions of stock, transactions with affiliates, and mergers and sales of assets.

6.75% Senior Notes due 2027

In November 2019, the Company issued $500.0 million aggregate principal amount of it 6.75% Senior Notes due December 2027 (the “2027 Notes”), which are subordinate to the 2023 Credit Agreement borrowings. The 2027 Notes are unsecured obligations and are guaranteed by certain of the Company’s domestic subsidiaries. Interest on the 2027 Notes is due semi-annually in June and December. The 2027 Notes mature on December 1, 2027 and are subordinated to all existing and future indebtedness.

The indenture governing the 2027 Notes contains covenants limiting other indebtedness, dividends, purchases or redemptions of stock, transactions with affiliates, and mergers and sales of assets.

Accounts Receivable Securitization Facility

On June 30, 2020, certain of the Company’s U.S. subsidiaries entered into a three-year committed revolving accounts receivable financing facility (the “AR Facility”) of up to $100.0 million with PNC Bank, National Association (“PNC”), as administrative agent and lender, and PNC Capital markets, LLC, as structuring agent. The AR Facility was further amended by the First Amendment to the AR Facility, dated as of June 27, 2022, the Second Amendment to the AR Facility, dated as of January 31, 2023, the Third Amended to the AR Facility, dated as of March 27, 2024 (extending the AR facility to March 2027), the Fourth Amended to the AR Facility, dated as of August 12, 2024, and the Fifth Amendment to the AR Facility, dated as of September 13, 2024.

In connection with the AR Facility, one of the Company’s U.S. subsidiaries, from time to time, sells and contributes receivables and certain related assets to a special purposes entity and wholly-owned U.S. subsidiary of the Company (the “SPE”). The SPE finances its acquisition of the receivables by obtaining secured loans from PNC and the other lenders party to a receivables financing agreement. A U.S. subsidiary of the Company services the receivables on behalf of the SPE for a fee. In addition, the Company has agreed to guarantee the performance by its subsidiaries. The Company and its subsidiaries do not guarantee the loan principal or interest under the receivables financing agreement or the collectability of the receivables under the AR Facility.

Amended and Restated Credit Agreement

The Company is party to its 2023 Credit Agreement, dated April 20, 2016 (as amended and restated as of November 26, 2019, as amended and restated as of May 5, 2023, as further amended by the First Amendment to the Credit Agreement, dated as March 27, 2024, the Second Amendment to the Credit Agreement, dated as of August 12, 2024, the Third Amendment to the Credit Agreement, dated as of September 13, 2024, the Fourth Amendment to the Credit Agreement, dated as of December 12, 2024, and the Fifth Amendment, dated as of June 16, 2025), (together the “Amended and Restated 2023 Credit Agreement”).

The Fifth Amendment, dated as of June 16, 2025 under the Amended and Restated 2023 Credit Agreement, among other things, fixed the aggregate revolving commitments at $325.0 million. The revolving credit facility under the Amended and Restated 2023 Credit Agreement is secured by substantially all existing and future U.S. assets of the Company, the Goderich mine in Ontario, Canada, and capital stock of certain subsidiaries.

As of December 31, 2025, the Company had borrowings of $10.0 million outstanding under the revolving credit facility. Also, as of December 31, 2025, outstanding letters of credit totaling $20.0 million further reduced the available borrowing capacity under the Company’s $325.0 million revolving credit facility to $295.0 million. Borrowings, if any, accrue interest at a rate per annum based on, at the Company’s option, the Adjusted Term SOFR Rate, Adjusted EURIBO Rate, Canadian Prime Rate, or Sterling Overnight Index Average, plus applicable margin. As of December 31, 2025, the weighted average interest rate on the revolving credit facility borrowings under the Amended and Restated 2023 Credit Agreement was approximately 6.5%.

Covenant Compliance

As of December 31, 2025, the Company was in compliance with its covenants.
v3.25.4
COMMITMENTS AND CONTINGENCIES
 3 Months Ended
Dec. 31, 2025
Commitments and Contingencies Disclosure [Abstract]  
COMMITMENTS AND CONTINGENCIES COMMITMENTS AND CONTINGENCIES
The Company is subject to legal and administrative proceedings and claims of various types from the ordinary course of the Company’s business. If management believes that a loss arising from these actions is probable and can reasonably be estimated, the Company records the amount of the loss or the minimum estimated liability when the loss is estimated using a range and no point is more probable than another. As additional information becomes available, any potential liability related to these actions is assessed and the estimates are revised, if necessary.

Management cannot predict the outcome of legal claims and proceedings with certainty. Nevertheless, management believes that the outcome of legal proceedings and claims, which are pending or known to be threatened, even if determined adversely, will not, individually or in the aggregate, have a material adverse effect on the Company’s results of operations, cash flows or financial position given current insurance coverage, except as otherwise described in this Note 7.

On February 1, 2023, a shareholder derivative lawsuit was filed in the District of Kansas by an individual shareholder, purportedly on behalf of the Company. The lawsuit alleged that certain directors and executives breached their fiduciary duties to shareholders by failing to prevent the dissemination of misstatements and omissions from October 30, 2017 to November 18, 2018. On October 30, 2024, an additional shareholder derivative lawsuit was filed in the District of Kansas by an individual shareholder, purportedly on behalf of the Company. The lawsuit alleged that certain directors and executives breached their fiduciary duties to shareholders by willfully or recklessly causing the Company to make false and/or misleading statements and/or omissions of material fact from October 31, 2017 to October 21, 2022. On February 28, 2025, this matter was consolidated with the derivative matter filed on February 1, 2023. On May 27, 2025, the parties reached an agreement in principle to resolve the consolidated derivative lawsuit in exchange for the Company’s agreement to adopt certain corporate governance reforms. A motion for final approval of the settlement was filed with the court on September 2, 2025. On October 14, 2025, the court held a hearing at which it approved the settlement, including fees and expenses awarded to lead counsel and plaintiffs. Insurers for the defendant directors and executives thereafter made their respective payments for the full amount of the awarded fees and expenses pursuant to their commitments and in accordance with the court’s order and the settlement agreement.

On April 24, 2024, a putative securities class action was filed in the United States District Court for the District of Kansas. The complaint alleged that the Company and certain individuals made materially false and misleading statements regarding Fortress North America, the Company’s former fire retardant business, and that shareholders were damaged by these statements. On December 12, 2024, the court appointed lead plaintiff and counsel. Plaintiffs filed an Amended Complaint on February 10, 2025. The parties have executed the settlement agreement dated June 30, 2025, to resolve the matter, which settlement was consented to by the Company’s insurers. On January 7, 2026, the court granted final approval of the settlement for $4.9 million, of which approximately $1.0 million of the settlement was paid by the Company.

On October 30, 2024, a shareholder derivative lawsuit was brought against certain current and former officers and directors of the Company, purportedly on behalf of the Company. The lawsuit alleges that from November 29, 2023 to March 22, 2024, certain current and former officers and directors willfully or recklessly caused the Company to make false and/or misleading statements and/or omissions of material fact regarding the Company’s fire retardant business. On April 9, 2025, an additional derivative lawsuit was brought against certain current and former officers and directors of the Company, purportedly on behalf of the Company. The lawsuit alleges that certain current and former officers and directors caused Compass Minerals to make misleading statements regarding the Company’s fire retardant business. In an order dated June 3, 2025, the court consolidated the two derivative actions for the discovery phase of the actions. On July 30, 2025, the plaintiffs in the consolidated derivative action filed a verified amended consolidated shareholder derivative complaint asserting claims that certain statements made between February 8, 2023 and March 25, 2024 about the Company’s fire retardant business were false and/or misleading. The parties have executed a settlement agreement dated October 24, 2025, to resolve the derivative actions, subject to obtaining court approval. Pursuant to the settlement agreement, the Company will implement certain corporate governance reforms as specified therein, and the Company’s insurers have agreed to pay legal fees and expenses to plaintiffs’ counsel. The court granted preliminary approval of the settlement on December 10, 2025, and scheduled a hearing for final approval for February 20, 2026.

On October 25, 2024, the Company issued a recall for specific production lots of food-grade salt produced at its Goderich Plant following a customer report of a non-organic, foreign material in its product. The Company subsequently expanded the voluntary recall to include food products from the Goderich Plant between September 18, 2024 and November 6, 2024. The Company followed recall protocol and notified its BRCGS Global Standard for Food Safety certifying body, the Canadian Food Inspection Agency (“CFIA”) and the U.S. Food and Drug Administration (“FDA”). The Company has completed its investigation and continues to assess the scope and magnitude of asserted and potential customer claims related to the recall. At this time, based on currently available information and its applicable insurance coverage, the Company does not believe any incremental losses will have a material adverse effect on its results of operations or cash flows in future periods. The recall in
the United States, supervised by the FDA, is complete, and the matter is closed with FDA. The CFIA has conducted a follow-up inspection of the Goderich Plant to verify compliance with regulatory requirements and identified no non-compliances.
As of December 31, 2025 and September 30, 2025, the Company recorded liabilities of $53.7 million and $51.8 million, respectively, included in Accrued expenses and other current liabilities, and estimated insurance recoveries of $47.7 million and $47.0 million, respectively, included in Receivables, in the Condensed Consolidated Balance Sheets associated with the recall matters described above, in addition to all other legal, environmental, and administrative proceedings.
v3.25.4
OPERATING SEGMENTS
 3 Months Ended
Dec. 31, 2025
Segment Reporting [Abstract]  
OPERATING SEGMENTS OPERATING SEGMENTS
 
The Company’s reportable segments are strategic business units that offer different products and services, and each business requires different technology and marketing strategies. For the three months ended December 31, 2025 and December 31, 2024, the Company has presented two reportable segments in its Consolidated Financial Statements: Salt and Plant Nutrition. The Salt segment produces and markets salt, consisting primarily of sodium chloride and magnesium chloride, for use in road deicing for winter roadway safety and for dust control, food processing, water softening and other consumer, agricultural and industrial applications. The Plant Nutrition segment produces and markets various grades of SOP. The results of operations for the Company’s records management businesses are included in Corporate and Other in the tables below.

The chief operating decision maker (“CODM”) is the Company’s President and Chief Executive Officer. The primary measure of segment profit or loss used by the CODM to regularly evaluate performance, make key operating decisions and determine resource allocation of and among each operating segment is operating income.

Segment information is as follows (in millions):
Three Months Ended December 31, 2025SaltPlant
Nutrition
Corporate
& Other(a)
Total
Sales to external customers(b)
$331.5 $60.8 $3.8 $396.1 
Intersegment sales— 1.0 (1.0)— 
Shipping and handling cost103.8 8.3 — 112.1 
Product cost172.0 46.3 2.5 220.8 
Gross profit55.7 6.2 1.3 63.2 
Selling, general and administrative expenses6.6 0.8 19.2 26.6 
Operating income (loss)49.1 5.4 (17.9)36.6 
Depreciation, depletion and amortization18.1 7.4 0.9 26.4 
Total assets (as of end of period)1,020.1 360.1 146.5 1,526.7 
Capital expenditures17.0 5.2 0.6 22.8 
Three Months Ended December 31, 2024SaltPlant
Nutrition
Corporate
& Other(a)
Total
Sales to external customers(b)
$242.2 $61.4 $3.6 $307.2 
Intersegment sales— 3.2 (3.2)— 
Shipping and handling cost71.3 9.3 — 80.6 
Product cost134.1 54.4 3.8 192.3 
Gross profit (loss)36.8 (2.3)(0.2)34.3 
Selling, general and administrative expenses7.4 0.8 25.1 33.3 
Other operating expense— — 0.5 0.5 
Operating income (loss)29.4 (3.1)(25.8)0.5 
Depreciation, depletion and amortization17.5 7.5 1.8 26.8 
Total assets (as of end of period)1,092.4 388.1 240.4 1,720.9 
Capital expenditures16.2 4.6 1.0 21.8 


Disaggregated revenue by product type is as follows (in millions):
Three Months Ended December 31, 2025SaltPlant
Nutrition
Corporate
& Other(a)
Total
Highway Deicing Salt$210.8 $— $— $210.8 
Consumer & Industrial Salt120.7 — — 120.7 
SOP— 61.8 — 61.8 
Eliminations & Other— (1.0)3.8 2.8 
Sales to external customers$331.5 $60.8 $3.8 $396.1 

Three Months Ended December 31, 2024SaltPlant
Nutrition
Corporate
& Other(a)
Total
Highway Deicing Salt$138.1 $— $— $138.1 
Consumer & Industrial Salt104.1 — — 104.1 
SOP— 64.6 — 64.6 
Eliminations & Other— (3.2)3.6 0.4 
Sales to external customers$242.2 $61.4 $3.6 $307.2 
(a)Corporate and Other includes corporate entities, records management operations and other incidental operations and eliminations. Operating income (loss) for corporate and other includes indirect corporate overhead, including costs for general corporate governance and oversight, as well as costs for the human resources, information technology, legal and finance functions.
(b)Sales to external customers are net of intersegment sales.
v3.25.4
STOCKHOLDERS’ EQUITY AND EQUITY INSTRUMENTS
 3 Months Ended
Dec. 31, 2025
Equity [Abstract]  
STOCKHOLDERS’ EQUITY AND EQUITY INSTRUMENTS STOCKHOLDERS’ EQUITY AND EQUITY INSTRUMENTS
Equity Compensation Awards

The 2020 Incentive Award Plan (as amended from time to time, the “2020 Plan”) provides for grants of equity awards to executive officers, other employees and directors, including restricted stock units (“RSUs”), performance stock units (“PSUs”), stock options, deferred stock units and other equity-based awards.

Stock-based compensation expense recorded in selling, general and administrative expenses in the Consolidated Statements of Operations was $2.3 million and $3.9 million for the three months ended December 31, 2025 and December 31, 2024, respectively. As of December 31, 2025, there was approximately $13.5 million of total estimated unrecognized compensation cost, assuming attainment of the performance target estimates, related to stock-based compensation arrangements expected to be recognized over a weighted average period of approximately 1.9 years.
Non-Employee Director Compensation. Non-employee directors may defer all or a portion of the fees payable for their service into deferred stock units, equivalent to the value of the Company’s common stock. The annual fees related to the director’s equity compensation were granted in deferred stock units or restricted stock units and will vest on the earlier of the day immediately preceding the Issuer's next annual meeting (as long as the meeting is held at least 50 weeks from the grant date) and the first anniversary of the grant date. In relation to these annual fees, the Company granted a pro-rata share of 5,392 RSUs to new directors during the three months ended December 31, 2025. Additionally, as dividends are declared on the Company’s common stock, these deferred stock units are entitled to accrete dividends in the form of additional units based on the stock price on the dividend payment date. Accumulated deferred stock units are distributed in the form of Company common stock at a future specified date or following resignation from the Board of Directors, based upon the director’s annual election. During the three months ended December 31, 2025, common shares of 6,641 were issued from treasury shares for director compensation related to quarterly fees payable and 2,260 deferred stock units.

RSUs. During the three months ended December 31, 2025, the Company granted 446,396 RSUs which vest after one to three years of service entitling the holders to one share of common stock for each vested RSU. The unvested RSUs do not have voting rights but are entitled to receive non-forfeitable dividends or other distributions that may be declared on the Company’s common stock equal to the per-share dividend declared. The closing stock price on the date of each grant was used to determine the fair value of RSUs.

PSUs. During the three months ended December 31, 2025, the Company granted 182,071 PSUs based upon certain performance criteria and metrics (“2026 Scorecard PSUs”). The actual number of shares of common stock that may be earned with respect to 2026 Scorecard PSUs is calculated based upon the attainment of certain thresholds for free cash flow and return on capital employed during each year of the three-year performance period and may range from 0% to 200% for each measure. Additionally, a modifier will increase or decrease the payout by 20% based upon relative total shareholder return against the Company’s peer group.

To estimate the fair value of the 2026 Scorecard PSUs on the grant date, the Company used a Monte-Carlo simulation model. This model uses historical stock prices to estimate expected volatility and the Company’s correlation to the peer group. The input for the expected stock price volatility was 48%. In addition, the Company used inputs for the risk-free rate of 3.5%, expected dividend yield of 0%, and the Company’s closing stock price on the grant date to estimate the fair value of the 2026 Scorecard PSUs. The Company will adjust the expense of the 2026 Scorecard PSUs based upon its estimate of the number of shares that will ultimately vest at each interim date during the vesting period.

Options. Substantially all of the stock options granted vest ratably, in tranches, over a four-year service period. Unexercised options expire after seven years. Options do not have dividend or voting rights. Upon vesting, each option can be exercised to purchase one share of the Company’s common stock.

The following table summarizes stock-based compensation activity during the three months ended December 31, 2025:
 Stock OptionsRSUs
PSUs(a)
 NumberWeighted-average
exercise price		NumberWeighted-average
fair value		NumberWeighted-average
fair value
Outstanding at September 30, 2025
107,261 $63.43 828,922 $15.34 316,480 $16.89 
Granted— — 446,396 17.83 182,071 19.37 
Released from restriction(b)
— — (185,719)17.07 — — 
Cancelled/expired(794)67.50 (781)15.85 — — 
Outstanding at December 31, 2025
106,467 $63.40 1,088,818 $16.11 498,551 $17.22 
(a)Until the performance period is completed, PSUs are included in the table at the target level at their grant date and at that target level represents one share of common stock per PSU.
(b)The Company paid taxes for restricted unit withholdings of approximately $1.2 million during the three months ended December 31, 2025.
Accumulated Other Comprehensive Loss (“AOCL”)

The Company’s comprehensive income (loss) is comprised of net loss, net amortization of the unrealized loss of the pension obligation, the change in the unrealized gain in other postretirement benefits, the change in the unrealized gain (loss) on natural gas and foreign currency cash flow hedges and currency translation adjustment (“CTA”). The components of and changes in AOCL are as follows (in millions):

Three Months Ended December 31, 2025(a)
Gains and (Losses) on Cash Flow HedgesDefined Benefit PensionOther Post-Employment BenefitsForeign CurrencyTotal
Beginning balance$(0.8)$(6.3)$1.8 $(102.6)$(107.9)
Other comprehensive loss before reclassifications(b)
(1.0)— — 7.0 6.0 
Amounts reclassified from AOCL(c)
0.5 0.2 — — 0.7 
Net current period other comprehensive income (loss)(0.5)0.2 — 7.0 6.7 
Ending balance$(1.3)$(6.1)$1.8 $(95.6)$(101.2)
(a)With the exception of the CTA, for which no tax effect is recorded, the changes in the components of AOCL presented in the tables above are reflected net of applicable income taxes.
(b)The Company recorded foreign exchange loss of $1.4 million in the three months ended December 31, 2025, in AOCL related to intercompany notes which were deemed to be of a long-term investment nature.
(c)The amounts reclassified from AOCL to expense (income) impacted the product cost line item in the Consolidated Statements of Operations.
v3.25.4
DERIVATIVE FINANCIAL INSTRUMENTS
 3 Months Ended
Dec. 31, 2025
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
DERIVATIVE FINANCIAL INSTRUMENTS DERIVATIVE FINANCIAL INSTRUMENTS
 
The Company is subject to various types of market risks, including interest rate risk, foreign currency exchange rate transaction and translation risk and commodity pricing risk. Management may take actions to mitigate the exposure to these types of risks, including entering into forward purchase contracts and other financial instruments. The Company manages a portion of its commodity pricing risks and foreign currency exchange rate risks by using derivative instruments. From time to time, the Company may enter into foreign exchange contracts to mitigate foreign exchange risk. The Company does not seek to engage in trading activities or take speculative positions with any financial instrument arrangement. The Company enters into natural gas derivative instruments and foreign currency derivative instruments with counterparties it views as creditworthy. However, the Company does attempt to mitigate its counterparty credit risk exposures by, among other things, entering into master netting agreements with some of these counterparties. The Company records derivative financial instruments as either assets or liabilities at fair value in its Condensed Consolidated Balance Sheets and the balances were not material as of December 31, 2025 and September 30, 2025.

Derivatives qualify for treatment as hedges when there is a high correlation between the change in fair value of the derivative instrument and the related change in value of the underlying hedged item. Depending on the exposure being hedged, the Company must designate the hedging instrument as a fair value hedge, a cash flow hedge or a net investment in foreign operations hedge. For the qualifying derivative instruments that have been designated as cash flow hedges, the effective portion of the change in fair value is recognized through earnings when the underlying transaction being hedged affects earnings, allowing a derivative’s gains and losses to offset related results from the hedged item in the Condensed Consolidated Statements of Operations. Any ineffectiveness related to these instruments accounted for as hedges was not material for any of the periods presented. For derivative instruments that have not been designated as hedges, the entire change in fair value is recorded through earnings in the period of change.

Natural Gas Derivative Instruments

Natural gas is consumed at several of the Company’s production facilities, and changes in natural gas prices impact the Company’s operating margin. The Company seeks to reduce the earnings and cash flow impacts of changes in market prices of natural gas by fixing the purchase price of up to 90% of its forecasted natural gas usage. It is the Company’s policy to consider hedging portions of its natural gas usage up to 36 months in advance of the forecasted purchase. As of December 31, 2025, the Company had entered into natural gas derivative instruments to hedge a portion of its natural gas purchase requirements through December 31, 2026. As of December 31, 2025 and September 30, 2025, the Company had agreements in place to hedge forecasted natural gas purchases of 2.0 million and 2.6 million MMBtus, respectively. All natural gas derivative instruments held by the Company as of December 31, 2025 and September 30, 2025 qualified and were designated as cash flow hedges. The Company recorded a net expense related to the natural gas cash flow hedges of $0.5 million and $0.6 million in
Product costs, during the three months ended December 31, 2025 and December 31, 2024, respectively. As of December 31, 2025, the Company expects to reclassify from AOCL to earnings during the next twelve months $1.3 million of net losses on derivative instruments related to its natural gas hedges. Refer to Note 11. Fair Value Measurements for the estimated fair value of the Company’s natural gas derivative instruments as of December 31, 2025.

The following tables present the fair value of the Company’s derivatives (in millions):
 Asset DerivativesLiability Derivatives
Consolidated Balance Sheet LocationDecember 31, 2025Consolidated Balance Sheet LocationDecember 31, 2025
Derivatives designated as hedging instruments:
Commodity contractsOther current assets$5.3 Accrued expenses and other current liabilities$6.6 
Commodity contractsOther assets0.1 Other noncurrent liabilities0.1 
Total derivatives(a)
$5.4 $6.7 
(a)The Company has master netting agreements with its commodity hedge counterparties and accordingly has netted in its Consolidated Balance Sheets $5.3 million of its commodity contracts that are in receivable positions against its contracts in payable positions.

 Asset DerivativesLiability Derivatives
Consolidated Balance Sheet LocationSeptember 30, 2025Consolidated Balance Sheet LocationSeptember 30, 2025
Derivatives designated as hedging instruments:
Commodity contractsOther current assets$6.2 Accrued expenses and other current liabilities$7.1 
Commodity contractsOther assets1.7 Other noncurrent liabilities1.6 
Total derivatives(a)
$7.9 $8.7 
(a)The Company has master netting agreements with its commodity hedge counterparties and accordingly has netted in its Condensed Consolidated Balance Sheets $7.8 million of its commodity contracts that are in receivable positions against its contracts in payable positions.

The following table presents activity related to accumulated other comprehensive (loss) income before taxes (in millions):

 Three Months Ended December 31, 2025
Derivatives in Cash Flow Hedging Relationships:Location of Change
Reclassified from
AOCL into Income
(Effective Portion)		Net Loss
Recognized in
AOCL on Derivatives
(Effective Portion)		Net Loss
Reclassified from
AOCL into
Income
(Effective Portion)
Commodity contractsProduct cost$(1.0)$0.5 
Total$(1.0)$0.5 
v3.25.4
FAIR VALUE MEASUREMENTS
 3 Months Ended
Dec. 31, 2025
Fair Value Disclosures [Abstract]  
FAIR VALUE MEASUREMENTS FAIR VALUE MEASUREMENTS
The Company’s financial instruments are measured and reported at their estimated fair values. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction. When available, the Company uses quoted prices in active markets to determine the fair values for its financial instruments (Level 1 inputs) or, absent quoted market prices, observable market-corroborated inputs over the term of the financial instruments (Level 2 inputs). The Company does not have any unobservable inputs that are not corroborated by market inputs (Level 3 inputs), except as stated below.
 
Recurring Fair Value Measurements

The following table summarizes the fair value hierarchy for each type of instrument carried at fair value on a recurring basis (in millions):
Fair Value Measurements at December 31, 2025 Using
 
Total Carrying Value at
December 31, 2025
Quoted Prices in Active Market
(Level One)		Significant Other Observable Inputs
(Level Two)		Significant Unobservable Inputs
(Level Three)
Asset Class:
Mutual fund investments in a non-qualified savings plan(a)(b)
$3.7 $3.7 $— $— 
Derivatives – natural gas instruments, net5.4 — 5.4 — 
Total assets at fair value$9.1 $3.7 $5.4 $— 
Liability Class:    
Derivatives - natural gas instruments, net$6.7 $— $6.7 $— 
Liabilities related to non-qualified savings plan3.7 3.7 — — 
Total liabilities at fair value$10.4 $3.7 $6.7 $— 
(a)Includes mutual fund investments of approximately 32% in common stock of large-cap U.S. companies, 4% in common stock of small to mid-cap U.S. companies, 3% in the common stock of international companies, 10% in bond funds, 16% in short-term investments, and 35% in blended funds.
(b)The investments related to a non-qualified deferred compensation arrangement on behalf of certain members of management. The Company has a liability for the related-party transaction recorded on Other noncurrent liabilities for deferred compensation obligation.

Valuation Techniques: The Company holds marketable securities associated with its deferred contribution and pre-tax savings plans, which are valued based on readily available quoted market prices. The Company utilizes derivative instruments to manage its risk of changes in natural gas prices and foreign exchange rates (see Note 10. Derivative Financial Instruments). The fair values of the natural gas and foreign currency derivative instruments are determined using market data of forward prices for all of the Company’s contracts. 

Other Fair Value Measurements

The Company is required to disclose the fair value of financial instruments that are not recognized at fair value in the statement of financial position for which it is practicable to estimate that value (in millions):

Fair Value Measurements at December 31, 2025 Using
 
Total Carrying Value at
December 31, 2025
Quoted Prices in Active Market
(Level One)		Significant Other Observable Inputs
(Level Two)		Significant Unobservable Inputs
(Level Three)
8.00% Senior Notes due July 2030
$650.0 $— $679.3 $— 
6.75% Senior Notes due December 2027
150.0 — 149.5 — 
Valuation Techniques: Observable market-based inputs were used to estimate fair value for Level 2 inputs, based on available trading information. Cash and cash equivalents, receivables (net of allowance for doubtful accounts) and accounts payable are carried at cost, which approximates fair value due to their liquid and short-term nature.
v3.25.4
NET INCOME (LOSS) PER SHARE
 3 Months Ended
Dec. 31, 2025
Earnings Per Share [Abstract]  
NET INCOME (LOSS) PER SHARE NET INCOME (LOSS) PER SHARE
 
Basic net income (loss) per share is computed by dividing net loss available to common stockholders by the weighted-average number of outstanding common shares during the period. Diluted net loss per share reflects the potential dilution that could occur under the more dilutive of either the treasury stock method or the two-class method for calculating the weighted-average number of outstanding common shares. Under the treasury stock method, potential shares of common shares outstanding are not included in the computation of diluted net (loss) income per share if their effect is anti-dilutive.
The following table sets forth the computation of basic and diluted net income (loss) per common share (in millions, except for share and per-share data):
 Three Months Ended
December 31,
 20252024
Numerator:
Net income (loss)$18.6 $(23.6)
Less: net income allocated to participating securities(a)
(0.3)— 
Net income (loss) available to common stockholders$18.3 $(23.6)
Denominator (in thousands):
Weighted-average common shares outstanding for basic net income (loss) per share42,083 41,441 
Weighted-average effect of dilutive equity awards outstanding184 — 
Shares for diluted net income (loss) per share(b)
42,267 41,441 
Basic net income (loss) per common share$0.43 $(0.57)
Diluted net income (loss) per common share$0.43 $(0.57)
(a)Weighted participating securities, consisting of RSUs that are entitled to non-forfeitable dividends if declared, totaled 693,000 and 1,116,000 for the three months ended December 31, 2025 and December 31, 2024, respectively.
(b)Weighted-average equity awards outstanding of 670,000 and 1,184,000, for the three months ended December 31, 2025 and December 31, 2024, respectively, were excluded from diluted net income (loss) per common share as they were anti-dilutive.
v3.25.4
RELATED PARTY TRANSACTIONS
 3 Months Ended
Dec. 31, 2025
Related Party Transactions [Abstract]  
RELATED PARTY TRANSACTIONS RELATED PARTY TRANSACTIONS
For the three months ended December 31, 2025 and December 31, 2024, the Company recorded approximately $0.5 million and $1.1 million, respectively, in SOP sales to certain subsidiaries of Koch Industries, Inc., which are considered related parties. As of both December 31, 2025 and September 30, 2025, the Company recorded approximately $0.2 million of receivables from related parties in its Condensed Consolidated Balance Sheets. The Company had no related-party payables outstanding as of December 31, 2025 and December 31, 2024.

Effective December 18, 2025, a new member was appointed to the Company’s board of directors. The new director also serves as President and Chief Executive Officer of another company from which the Company purchased approximately $1.1 million of salt-treatment materials during the three months ended December 31, 2025, constituting a related party transaction. In addition, the Company has a payable of approximately $0.3 million outstanding as of December 31, 2025, related to this transaction.
v3.25.4
Subsequent Events
 3 Months Ended
Dec. 31, 2025
Subsequent Events [Abstract]  
Subsequent Events SUBSEQUENT EVENT
On February 2, 2026, the Company entered into a share purchase agreement to sell its equity interest in its sulfate of potash specialty fertilizer (“SOP”) facility in Wynyard, Saskatchewan, Canada. The agreement provides for total cash consideration of approximately $30.8 million, subject to customary closing conditions and prior to any transaction costs. The cash proceeds payable at closing will be adjusted pursuant to the terms of the agreement, including working capital and other specified adjustments. This divestiture aligns with the Company’s continued initiative to strengthen its balance sheet and advance its debt-reduction efforts. The closing of the transaction will occur upon completion of the remaining closing conditions.
v3.25.4
Insider Trading Arrangements
 3 Months Ended
Dec. 31, 2025
Trading Arrangements, by Individual  
Rule 10b5-1 Arrangement Adopted false
Non-Rule 10b5-1 Arrangement Adopted false
Rule 10b5-1 Arrangement Terminated false
Non-Rule 10b5-1 Arrangement Terminated false
v3.25.4
ACCOUNTING POLICIES AND BASIS OF PRESENTATION (Policies)
 3 Months Ended
Dec. 31, 2025
Accounting Policies [Abstract]  
Basis of Consolidation
CMI is a holding company with no significant operations other than those of its wholly-owned subsidiaries. The consolidated financial statements include the accounts of CMI and its wholly-owned domestic and foreign subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.
Basis of Presentation
The accompanying condensed consolidated balance sheet as of September 30, 2025, which was derived from audited financial statements, and the unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete consolidated financial statements. As a result, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2025 (“2025-K”). In the opinion of management, these interim financial statements reflect all adjustments, consisting of normal recurring adjustments considered necessary for a fair presentation of the Company’s financial position and results of operations.
Accounting Pronouncements Issued Not Yet Adopted
Accounting Pronouncements Issued Not Yet Adopted

Income Tax Disclosures. In December 2023, the Financial Accounting Standards Board (“FASB”) issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which updates income tax disclosures by requiring consistent categories and additional disaggregation of information in the rate reconciliation and income taxes paid by jurisdiction. The ASU is effective for fiscal years beginning after December 15, 2024, and is effective for the Company beginning in the annual report for the fiscal year ended September 30, 2026. Early adoption is permitted. The amendments should be applied prospectively; however, retrospective application is permitted. Management is currently evaluating this ASU to determine its impact on the Company’s disclosures.

Disaggregation of Income Statement Expenses. In November 2024, the FASB issued amended guidance related to disclosure of disaggregated expenses (“ASU 2024-03”). This amendment requires public business entities to provide detailed disclosures in the notes to financial statements disaggregating specific expense categories, including employee compensation, depreciation, and intangible asset amortization, as well as certain other disclosures to provide enhanced transparency into the nature and function of expenses. This guidance is effective for annual periods beginning in the Company’s annual report for the fiscal year ended September 30, 2028 and interim periods following annual adoption, with early adoption permitted. This guidance will be applied on a prospective basis with retrospective application permitted. Management is currently evaluating ASU 2024-03 to determine its impact on the Company’s disclosures.

Interim Reporting. In December 2025, the FASB issued ASU 2025-11, Interim Reporting (Topic 270): Narrow-Scope Improvements (“ASU 2025-11”), to improve the guidance for interim reporting and clarify when that guidance is applicable. This ASU provides a comprehensive list of required interim disclosures and also requires entities to disclose events since the end of the last annual reporting period that have a material impact on the entity. ASU 2025-11 is effective for interim reporting periods within annual reporting periods beginning after December 15, 2027. For the Company, the guidance becomes effective in the first interim period of the fiscal year ended September 30, 2029. Early adoption is permitted. Management is currently evaluating ASU 2025-11 to determine its impact on the Company’s disclosures.
Deferred Revenue
Deferred Revenue
Deferred revenue represents collections under non-cancellable contracts before the related product or service is transferred to the customer. The portion of deferred revenue that is anticipated to be recognized as revenue during the succeeding twelve-month period is recorded in accrued expenses and other current liabilities on the Consolidated Balance Sheets.
Derivative Financial Instruments
The Company is subject to various types of market risks, including interest rate risk, foreign currency exchange rate transaction and translation risk and commodity pricing risk. Management may take actions to mitigate the exposure to these types of risks, including entering into forward purchase contracts and other financial instruments. The Company manages a portion of its commodity pricing risks and foreign currency exchange rate risks by using derivative instruments. From time to time, the Company may enter into foreign exchange contracts to mitigate foreign exchange risk. The Company does not seek to engage in trading activities or take speculative positions with any financial instrument arrangement. The Company enters into natural gas derivative instruments and foreign currency derivative instruments with counterparties it views as creditworthy. However, the Company does attempt to mitigate its counterparty credit risk exposures by, among other things, entering into master netting agreements with some of these counterparties. The Company records derivative financial instruments as either assets or liabilities at fair value in its Condensed Consolidated Balance Sheets and the balances were not material as of December 31, 2025 and September 30, 2025.
Derivatives qualify for treatment as hedges when there is a high correlation between the change in fair value of the derivative instrument and the related change in value of the underlying hedged item. Depending on the exposure being hedged, the Company must designate the hedging instrument as a fair value hedge, a cash flow hedge or a net investment in foreign operations hedge. For the qualifying derivative instruments that have been designated as cash flow hedges, the effective portion of the change in fair value is recognized through earnings when the underlying transaction being hedged affects earnings, allowing a derivative’s gains and losses to offset related results from the hedged item in the Condensed Consolidated Statements of Operations. Any ineffectiveness related to these instruments accounted for as hedges was not material for any of the periods presented. For derivative instruments that have not been designated as hedges, the entire change in fair value is recorded through earnings in the period of change.
v3.25.4
REVENUES (Tables)
 3 Months Ended
Dec. 31, 2025
Revenue from Contract with Customer [Abstract]  
Schedule of Balances of Receivables
The following table provides the balances of receivables (in millions):
 December 31,
2025		September 30,
2025
Current Assets:
Receivables related to contracts with customers
$226.4 $127.3 
Miscellaneous receivables(a)
52.2 52.3 
Total receivables
$278.6 $179.6 
(a)Refer to Note 7. Commitments and Contingencies for additional information.
Schedule of Revenue Recognition
Revenue is disaggregated in the following table by timing of revenue recognition (in millions):
 Three Months Ended
December 31,
 20252024
Timing of revenue recognition:
Products and services transferred at a point in time$393.3 $304.6 
Products and services transferred over time(a)
2.8 2.6 
Total revenues$396.1 $307.2 
(a)     Amounts include records management business utilizing excavated areas of its Winsford salt mine with one other location in London, England.
Disaggregated revenue by product type is as follows (in millions):
Three Months Ended December 31, 2025SaltPlant
Nutrition
Corporate
& Other(a)
Total
Highway Deicing Salt$210.8 $— $— $210.8 
Consumer & Industrial Salt120.7 — — 120.7 
SOP— 61.8 — 61.8 
Eliminations & Other— (1.0)3.8 2.8 
Sales to external customers$331.5 $60.8 $3.8 $396.1 

Three Months Ended December 31, 2024SaltPlant
Nutrition
Corporate
& Other(a)
Total
Highway Deicing Salt$138.1 $— $— $138.1 
Consumer & Industrial Salt104.1 — — 104.1 
SOP— 64.6 — 64.6 
Eliminations & Other— (3.2)3.6 0.4 
Sales to external customers$242.2 $61.4 $3.6 $307.2 
(a)Corporate and Other includes corporate entities, records management operations and other incidental operations and eliminations. Operating income (loss) for corporate and other includes indirect corporate overhead, including costs for general corporate governance and oversight, as well as costs for the human resources, information technology, legal and finance functions.
(b)Sales to external customers are net of intersegment sales.
v3.25.4
INVENTORIES (Tables)
 3 Months Ended
Dec. 31, 2025
Inventory Disclosure [Abstract]  
Schedule of Inventories
Inventories consist of the following (in millions):
 December 31,
2025		September 30,
2025
Finished goods$162.5 $219.1 
Work in process5.9 5.9 
Raw materials and supplies(a)
90.0 87.0 
Total inventories$258.4 $312.0 
(a)Excludes certain raw materials and supplies of $33.2 million and $33.0 million as of December 31, 2025 and September 30, 2025, respectively, that are not expected to be consumed within the next twelve months, included in Other noncurrent assets in the Condensed Consolidated Balance Sheets.
v3.25.4
PROPERTY, PLANT AND EQUIPMENT, NET (Tables)
 3 Months Ended
Dec. 31, 2025
Property, Plant and Equipment [Abstract]  
Schedule of Property, Plant and Equipment, Net
Property, plant and equipment, net, consists of the following (in millions):
 December 31,
2025		September 30,
2025
Land, buildings and structures, and leasehold improvements$559.1 $554.1 
Machinery and equipment1,171.9 1,154.9 
Office furniture and equipment24.0 23.9 
Mineral interests169.8 169.1 
Construction in progress53.5 51.6 
 1,978.3 1,953.6 
Less: accumulated depreciation and depletion(1,212.1)(1,183.5)
Property, plant and equipment, net$766.2 $770.1 
Schedule of Cash Flow, Supplemental Disclosures
The following table provides supplemental non-cash activities (in million):
Three Months Ended
December 31,
 20252024
Purchases of Property, plant and equipment in Accounts payable$5.5 $2.7 
Purchases of Property, plant and equipment in Accrued expenses and other current liabilities4.4 4.0 
Transfers of Property, plant and equipment from Inventory3.1 0.4 
v3.25.4
LONG-TERM DEBT AND FINANCE LEASE LIABILITIES (Tables)
 3 Months Ended
Dec. 31, 2025
Debt Disclosure [Abstract]  
Schedule of Total Long-Term Carrying Value of Debt and Finance Lease Liabilities
Total long-term carrying value of debt and finance lease liabilities consists of the following (in millions):
 December 31,
2025		September 30,
2025
Secured Debt:
Revolving Credit Facility due May 2028$10.0 $— 
Subordinated Debt:
8.00% Senior Notes due July 2030
650.0 650.0 
6.75% Senior Notes due December 2027
150.0 150.0 
Accounts Receivable Securitization Facility expires March 202786.5 45.8 
Total principal amount of debt896.5 845.8 
Finance lease liabilities13.3 15.5 
Unamortized deferred financing costs(12.9)(13.6)
Total carrying value of debt and finance lease liabilities896.9 847.7 
Current portion of finance lease liabilities(6.9)(7.9)
Total long-term carrying value of debt and finance lease liabilities$890.0 $839.8 
v3.25.4
OPERATING SEGMENTS (Tables)
 3 Months Ended
Dec. 31, 2025
Segment Reporting [Abstract]  
Schedule of Segment Information
Segment information is as follows (in millions):
Three Months Ended December 31, 2025SaltPlant
Nutrition
Corporate
& Other(a)
Total
Sales to external customers(b)
$331.5 $60.8 $3.8 $396.1 
Intersegment sales— 1.0 (1.0)— 
Shipping and handling cost103.8 8.3 — 112.1 
Product cost172.0 46.3 2.5 220.8 
Gross profit55.7 6.2 1.3 63.2 
Selling, general and administrative expenses6.6 0.8 19.2 26.6 
Operating income (loss)49.1 5.4 (17.9)36.6 
Depreciation, depletion and amortization18.1 7.4 0.9 26.4 
Total assets (as of end of period)1,020.1 360.1 146.5 1,526.7 
Capital expenditures17.0 5.2 0.6 22.8 
Three Months Ended December 31, 2024SaltPlant
Nutrition
Corporate
& Other(a)
Total
Sales to external customers(b)
$242.2 $61.4 $3.6 $307.2 
Intersegment sales— 3.2 (3.2)— 
Shipping and handling cost71.3 9.3 — 80.6 
Product cost134.1 54.4 3.8 192.3 
Gross profit (loss)36.8 (2.3)(0.2)34.3 
Selling, general and administrative expenses7.4 0.8 25.1 33.3 
Other operating expense— — 0.5 0.5 
Operating income (loss)29.4 (3.1)(25.8)0.5 
Depreciation, depletion and amortization17.5 7.5 1.8 26.8 
Total assets (as of end of period)1,092.4 388.1 240.4 1,720.9 
Capital expenditures16.2 4.6 1.0 21.8 
Schedule of Disaggregated Revenue by Product Type
Revenue is disaggregated in the following table by timing of revenue recognition (in millions):
 Three Months Ended
December 31,
 20252024
Timing of revenue recognition:
Products and services transferred at a point in time$393.3 $304.6 
Products and services transferred over time(a)
2.8 2.6 
Total revenues$396.1 $307.2 
(a)     Amounts include records management business utilizing excavated areas of its Winsford salt mine with one other location in London, England.
Disaggregated revenue by product type is as follows (in millions):
Three Months Ended December 31, 2025SaltPlant
Nutrition
Corporate
& Other(a)
Total
Highway Deicing Salt$210.8 $— $— $210.8 
Consumer & Industrial Salt120.7 — — 120.7 
SOP— 61.8 — 61.8 
Eliminations & Other— (1.0)3.8 2.8 
Sales to external customers$331.5 $60.8 $3.8 $396.1 

Three Months Ended December 31, 2024SaltPlant
Nutrition
Corporate
& Other(a)
Total
Highway Deicing Salt$138.1 $— $— $138.1 
Consumer & Industrial Salt104.1 — — 104.1 
SOP— 64.6 — 64.6 
Eliminations & Other— (3.2)3.6 0.4 
Sales to external customers$242.2 $61.4 $3.6 $307.2 
(a)Corporate and Other includes corporate entities, records management operations and other incidental operations and eliminations. Operating income (loss) for corporate and other includes indirect corporate overhead, including costs for general corporate governance and oversight, as well as costs for the human resources, information technology, legal and finance functions.
(b)Sales to external customers are net of intersegment sales.
v3.25.4
STOCKHOLDERS’ EQUITY AND EQUITY INSTRUMENTS (Tables)
 3 Months Ended
Dec. 31, 2025
Equity [Abstract]  
Schedule of Stock-Based Compensation Activity
The following table summarizes stock-based compensation activity during the three months ended December 31, 2025:
 Stock OptionsRSUs
PSUs(a)
 NumberWeighted-average
exercise price		NumberWeighted-average
fair value		NumberWeighted-average
fair value
Outstanding at September 30, 2025
107,261 $63.43 828,922 $15.34 316,480 $16.89 
Granted— — 446,396 17.83 182,071 19.37 
Released from restriction(b)
— — (185,719)17.07 — — 
Cancelled/expired(794)67.50 (781)15.85 — — 
Outstanding at December 31, 2025
106,467 $63.40 1,088,818 $16.11 498,551 $17.22 
(a)Until the performance period is completed, PSUs are included in the table at the target level at their grant date and at that target level represents one share of common stock per PSU.
(b)The Company paid taxes for restricted unit withholdings of approximately $1.2 million during the three months ended December 31, 2025.
Schedule of Components and Changes in Accumulated Other Comprehensive Income (Loss) The components of and changes in AOCL are as follows (in millions):
Three Months Ended December 31, 2025(a)
Gains and (Losses) on Cash Flow HedgesDefined Benefit PensionOther Post-Employment BenefitsForeign CurrencyTotal
Beginning balance$(0.8)$(6.3)$1.8 $(102.6)$(107.9)
Other comprehensive loss before reclassifications(b)
(1.0)— — 7.0 6.0 
Amounts reclassified from AOCL(c)
0.5 0.2 — — 0.7 
Net current period other comprehensive income (loss)(0.5)0.2 — 7.0 6.7 
Ending balance$(1.3)$(6.1)$1.8 $(95.6)$(101.2)
(a)With the exception of the CTA, for which no tax effect is recorded, the changes in the components of AOCL presented in the tables above are reflected net of applicable income taxes.
(b)The Company recorded foreign exchange loss of $1.4 million in the three months ended December 31, 2025, in AOCL related to intercompany notes which were deemed to be of a long-term investment nature.
(c)The amounts reclassified from AOCL to expense (income) impacted the product cost line item in the Consolidated Statements of Operations.
v3.25.4
DERIVATIVE FINANCIAL INSTRUMENTS (Tables)
 3 Months Ended
Dec. 31, 2025
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Schedule of Fair Value of Derivatives
The following tables present the fair value of the Company’s derivatives (in millions):
 Asset DerivativesLiability Derivatives
Consolidated Balance Sheet LocationDecember 31, 2025Consolidated Balance Sheet LocationDecember 31, 2025
Derivatives designated as hedging instruments:
Commodity contractsOther current assets$5.3 Accrued expenses and other current liabilities$6.6 
Commodity contractsOther assets0.1 Other noncurrent liabilities0.1 
Total derivatives(a)
$5.4 $6.7 
(a)The Company has master netting agreements with its commodity hedge counterparties and accordingly has netted in its Consolidated Balance Sheets $5.3 million of its commodity contracts that are in receivable positions against its contracts in payable positions.

 Asset DerivativesLiability Derivatives
Consolidated Balance Sheet LocationSeptember 30, 2025Consolidated Balance Sheet LocationSeptember 30, 2025
Derivatives designated as hedging instruments:
Commodity contractsOther current assets$6.2 Accrued expenses and other current liabilities$7.1 
Commodity contractsOther assets1.7 Other noncurrent liabilities1.6 
Total derivatives(a)
$7.9 $8.7 
(a)The Company has master netting agreements with its commodity hedge counterparties and accordingly has netted in its Condensed Consolidated Balance Sheets $7.8 million of its commodity contracts that are in receivable positions against its contracts in payable positions.
Schedule of Activity Related to Accumulated Other Comprehensive (Loss) Income Before Taxes
The following table presents activity related to accumulated other comprehensive (loss) income before taxes (in millions):

 Three Months Ended December 31, 2025
Derivatives in Cash Flow Hedging Relationships:Location of Change
Reclassified from
AOCL into Income
(Effective Portion)		Net Loss
Recognized in
AOCL on Derivatives
(Effective Portion)		Net Loss
Reclassified from
AOCL into
Income
(Effective Portion)
Commodity contractsProduct cost$(1.0)$0.5 
Total$(1.0)$0.5 
v3.25.4
FAIR VALUE MEASUREMENTS (Tables)
 3 Months Ended
Dec. 31, 2025
Fair Value Disclosures [Abstract]  
Schedule of Estimated Fair Values for Type of Instrument
The following table summarizes the fair value hierarchy for each type of instrument carried at fair value on a recurring basis (in millions):
Fair Value Measurements at December 31, 2025 Using
 
Total Carrying Value at
December 31, 2025
Quoted Prices in Active Market
(Level One)		Significant Other Observable Inputs
(Level Two)		Significant Unobservable Inputs
(Level Three)
Asset Class:
Mutual fund investments in a non-qualified savings plan(a)(b)
$3.7 $3.7 $— $— 
Derivatives – natural gas instruments, net5.4 — 5.4 — 
Total assets at fair value$9.1 $3.7 $5.4 $— 
Liability Class:    
Derivatives - natural gas instruments, net$6.7 $— $6.7 $— 
Liabilities related to non-qualified savings plan3.7 3.7 — — 
Total liabilities at fair value$10.4 $3.7 $6.7 $— 
(a)Includes mutual fund investments of approximately 32% in common stock of large-cap U.S. companies, 4% in common stock of small to mid-cap U.S. companies, 3% in the common stock of international companies, 10% in bond funds, 16% in short-term investments, and 35% in blended funds.
(b)The investments related to a non-qualified deferred compensation arrangement on behalf of certain members of management. The Company has a liability for the related-party transaction recorded on Other noncurrent liabilities for deferred compensation obligation.
The Company is required to disclose the fair value of financial instruments that are not recognized at fair value in the statement of financial position for which it is practicable to estimate that value (in millions):

Fair Value Measurements at December 31, 2025 Using
 
Total Carrying Value at
December 31, 2025
Quoted Prices in Active Market
(Level One)		Significant Other Observable Inputs
(Level Two)		Significant Unobservable Inputs
(Level Three)
8.00% Senior Notes due July 2030
$650.0 $— $679.3 $— 
6.75% Senior Notes due December 2027
150.0 — 149.5 — 
v3.25.4
NET INCOME (LOSS) PER SHARE (Tables)
 3 Months Ended
Dec. 31, 2025
Earnings Per Share [Abstract]  
Schedule of Computation of Basic and Diluted Earnings (Loss) Per Common Share
The following table sets forth the computation of basic and diluted net income (loss) per common share (in millions, except for share and per-share data):
 Three Months Ended
December 31,
 20252024
Numerator:
Net income (loss)$18.6 $(23.6)
Less: net income allocated to participating securities(a)
(0.3)— 
Net income (loss) available to common stockholders$18.3 $(23.6)
Denominator (in thousands):
Weighted-average common shares outstanding for basic net income (loss) per share42,083 41,441 
Weighted-average effect of dilutive equity awards outstanding184 — 
Shares for diluted net income (loss) per share(b)
42,267 41,441 
Basic net income (loss) per common share$0.43 $(0.57)
Diluted net income (loss) per common share$0.43 $(0.57)
(a)Weighted participating securities, consisting of RSUs that are entitled to non-forfeitable dividends if declared, totaled 693,000 and 1,116,000 for the three months ended December 31, 2025 and December 31, 2024, respectively.
(b)Weighted-average equity awards outstanding of 670,000 and 1,184,000, for the three months ended December 31, 2025 and December 31, 2024, respectively, were excluded from diluted net income (loss) per common share as they were anti-dilutive.
v3.25.4
REVENUES - Schedule of Revenue Recognition (Details) - USD ($)
$ in Millions
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Disaggregation of Revenue [Line Items]    
Total revenues $ 396.1 $ 307.2
Products and services transferred at a point in time    
Disaggregation of Revenue [Line Items]    
Total revenues 393.3 304.6
Products and services transferred over time    
Disaggregation of Revenue [Line Items]    
Total revenues $ 2.8 $ 2.6
v3.25.4
REVENUES - Schedule of Balances of Receivables (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Sep. 30, 2025
Current Assets:    
Receivables related to contracts with customers $ 226.4 $ 127.3
Miscellaneous receivables 52.2 52.3
Total receivables $ 278.6 $ 179.6
v3.25.4
REVENUES - Narrative (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Sep. 30, 2025
Revenue from Contract with Customer [Abstract]    
Deferred revenue $ 1.6 $ 1.6
v3.25.4
INVENTORIES (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Sep. 30, 2025
Inventory Disclosure [Abstract]    
Finished goods $ 162.5 $ 219.1
Work in process 5.9 5.9
Raw materials and supplies 90.0 87.0
Total inventories 258.4 312.0
Raw materials and supplies, noncurrent $ 33.2 $ 33.0
v3.25.4
PROPERTY, PLANT AND EQUIPMENT, NET - Schedule of Property, Plant and Equipment, Net (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Sep. 30, 2025
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 1,978.3 $ 1,953.6
Less: accumulated depreciation and depletion (1,212.1) (1,183.5)
Property, plant and equipment, net 766.2 770.1
Land, buildings and structures, and leasehold improvements    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 559.1 554.1
Machinery and equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 1,171.9 1,154.9
Office furniture and equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 24.0 23.9
Mineral interests    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 169.8 169.1
Construction in progress    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 53.5 $ 51.6
v3.25.4
PROPERTY, PLANT AND EQUIPMENT, NET - Schedule of Supplemental Non-Cash Activities (Details) - USD ($)
$ in Millions
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Property, Plant and Equipment [Abstract]    
Purchases of Property, plant and equipment in Accounts payable $ 5.5 $ 2.7
Purchases of Property, plant and equipment in Accrued expenses and other current liabilities 4.4 4.0
Transfers of Property, plant and equipment from Inventory $ 3.1 $ 0.4
v3.25.4
INCOME TAXES (Details) - USD ($)
$ in Millions
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Sep. 30, 2025
Income Tax Disclosure [Line Items]      
Nondeductible executive compensation $ 1.0    
Decrease in cash 13.0 $ (25.6)  
Income tax benefit (expense) (2.2) $ 9.7  
Foreign Tax Authority      
Income Tax Disclosure [Line Items]      
Net operating loss carryforwards 80.5   $ 80.5
Decrease in cash 24.8    
Increase in other current assets 21.9    
Decrease in other noncurrent assets 47.1    
Decrease in other noncurrent liabilities 56.2    
Foreign Tax Authority | Canadian Tax Authority      
Income Tax Disclosure [Line Items]      
Total reassessments including interest 209.8    
Payment for tax settlement 8.2    
Amount of security posted in the form of cash 35.8   35.8
Income tax benefit (expense) 6.2    
Amount of security posted in the form of a performance bond 157.4    
State and Local | NOL Carryforwards Expire Beginning in 2035      
Income Tax Disclosure [Line Items]      
Net operating loss carryforwards $ 7.1   $ 7.1
v3.25.4
LONG-TERM DEBT AND FINANCE LEASE LIABILITIES - Schedule of Long-Term Debt and Finance Lease Liabilities (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Sep. 30, 2025
Jun. 16, 2025
Nov. 30, 2019
Debt Instrument [Line Items]        
Total principal amount of debt $ 896.5 $ 845.8    
Finance lease liabilities 13.3 15.5    
Unamortized deferred financing costs (12.9) (13.6)    
Total carrying value of debt and finance lease liabilities 896.9 847.7    
Current portion of finance lease liabilities (6.9) (7.9)    
Total long-term carrying value of debt and finance lease liabilities $ 890.0 839.8    
Senior Notes | 0.08 Senior Notes due July 2030        
Debt Instrument [Line Items]        
Stated interest rate 8.00%   8.00%  
Total principal amount of debt $ 650.0 650.0    
Senior Notes | 6.75% Senior Notes due December 2027        
Debt Instrument [Line Items]        
Stated interest rate 6.75%     6.75%
Total principal amount of debt $ 150.0 150.0    
Line of Credit | Revolving Credit Facility due May 2028        
Debt Instrument [Line Items]        
Total principal amount of debt 10.0 0.0    
Line of Credit | Accounts Receivable Securitization Facility expires March 2027        
Debt Instrument [Line Items]        
Total principal amount of debt $ 86.5 $ 45.8    
v3.25.4
LONG-TERM DEBT AND FINANCE LEASE LIABILITIES - Narrative (Details) - USD ($)
Jun. 16, 2025
Jun. 30, 2020
Dec. 31, 2025
Nov. 30, 2019
Unallocated Financing Receivables | Account Receivable Financing Receivable        
Debt Instrument [Line Items]        
Financing receivable, term   3 years    
Revolving accounts receivable financing facility   $ 100,000,000    
Senior Notes | 0.08 Senior Notes due July 2030        
Debt Instrument [Line Items]        
Stated interest rate 8.00%   8.00%  
Aggregate principal amount $ 650,000,000      
Debt issuance costs $ 13,000,000      
Debt instrument, term 5 years      
Senior Notes | 6.75% Senior Notes due December 2027        
Debt Instrument [Line Items]        
Stated interest rate     6.75% 6.75%
Aggregate principal amount       $ 500,000,000
Line of Credit | 2023 Credit Agreement | Revolving Credit Facility        
Debt Instrument [Line Items]        
Weighted average interest rate of debt (as a percent)     6.50%  
Line of Credit | Amended And Restated 2023 Credit Agreement | Revolving Credit Facility        
Debt Instrument [Line Items]        
Aggregate principal amount of credit facility $ 325,000,000      
Outstanding borrowing     $ 10,000,000  
Availability under revolving credit facility     295,000,000.0  
Line of Credit | Amended And Restated 2023 Credit Agreement | Letter of Credit        
Debt Instrument [Line Items]        
Outstanding borrowing     $ 20,000,000.0  
v3.25.4
COMMITMENTS AND CONTINGENCIES (Details)
$ in Millions
Jan. 07, 2026
USD ($)
Dec. 31, 2025
USD ($)
Sep. 30, 2025
USD ($)
Jun. 03, 2025
action
Loss Contingencies [Line Items]        
Number of actions | action       2
Loss contingency liability   $ 53.7 $ 51.8  
Estimated insurance recoveries   $ 47.7 $ 47.0  
Subsequent Event        
Loss Contingencies [Line Items]        
Litigation settlement, amount awarded to other party $ 4.9      
Payments for Legal Settlements $ 1.0      
v3.25.4
OPERATING SEGMENTS - Narrative (Details) - segment
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Segment Reporting [Abstract]    
Number of reportable segments 2 2
v3.25.4
OPERATING SEGMENTS - Schedule of Segment Information (Details) - USD ($)
$ in Millions
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Segment Reporting Information [Line Items]    
Sales $ 396.1 $ 307.2
Gross profit 63.2 34.3
Selling, general and administrative expenses 26.6 33.3
Other operating expense   0.5
Operating income (loss) 36.6 0.5
Depreciation, depletion and amortization 26.4 26.8
Total assets (as of end of period) 1,526.7 1,720.9
Capital expenditures 22.8 21.8
Shipping and handling cost    
Segment Reporting Information [Line Items]    
Cost 112.1 80.6
Product cost    
Segment Reporting Information [Line Items]    
Cost 220.8 192.3
Operating Segments | Salt    
Segment Reporting Information [Line Items]    
Sales 331.5 242.2
Gross profit 55.7 36.8
Selling, general and administrative expenses 6.6 7.4
Other operating expense   0.0
Operating income (loss) 49.1 29.4
Depreciation, depletion and amortization 18.1 17.5
Total assets (as of end of period) 1,020.1 1,092.4
Capital expenditures 17.0 16.2
Operating Segments | Salt | Shipping and handling cost    
Segment Reporting Information [Line Items]    
Cost 103.8 71.3
Operating Segments | Salt | Product cost    
Segment Reporting Information [Line Items]    
Cost 172.0 134.1
Operating Segments | Plant Nutrition    
Segment Reporting Information [Line Items]    
Sales 60.8 61.4
Gross profit 6.2 (2.3)
Selling, general and administrative expenses 0.8 0.8
Other operating expense   0.0
Operating income (loss) 5.4 (3.1)
Depreciation, depletion and amortization 7.4 7.5
Total assets (as of end of period) 360.1 388.1
Capital expenditures 5.2 4.6
Operating Segments | Plant Nutrition | Shipping and handling cost    
Segment Reporting Information [Line Items]    
Cost 8.3 9.3
Operating Segments | Plant Nutrition | Product cost    
Segment Reporting Information [Line Items]    
Cost 46.3 54.4
Corporate & Other    
Segment Reporting Information [Line Items]    
Sales 3.8 3.6
Gross profit 1.3 (0.2)
Selling, general and administrative expenses 19.2 25.1
Other operating expense   0.5
Operating income (loss) (17.9) (25.8)
Depreciation, depletion and amortization 0.9 1.8
Total assets (as of end of period) 146.5 240.4
Capital expenditures 0.6 1.0
Corporate & Other | Shipping and handling cost    
Segment Reporting Information [Line Items]    
Cost 0.0 0.0
Corporate & Other | Product cost    
Segment Reporting Information [Line Items]    
Cost 2.5 3.8
Intersegment Eliminations    
Segment Reporting Information [Line Items]    
Sales (1.0) (3.2)
Intersegment Eliminations | Salt    
Segment Reporting Information [Line Items]    
Sales 0.0 0.0
Intersegment Eliminations | Plant Nutrition    
Segment Reporting Information [Line Items]    
Sales $ 1.0 $ 3.2
v3.25.4
OPERATING SEGMENTS - Schedule of Disaggregated Revenue by Product Type (Details) - USD ($)
$ in Millions
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Segment Reporting Information [Line Items]    
Sales to external customers $ 396.1 $ 307.2
Highway Deicing Salt    
Segment Reporting Information [Line Items]    
Sales to external customers 210.8 138.1
Consumer & Industrial Salt    
Segment Reporting Information [Line Items]    
Sales to external customers 120.7 104.1
SOP    
Segment Reporting Information [Line Items]    
Sales to external customers 61.8 64.6
Eliminations & Other    
Segment Reporting Information [Line Items]    
Sales to external customers 2.8 0.4
Operating Segments | Salt    
Segment Reporting Information [Line Items]    
Sales to external customers 331.5 242.2
Operating Segments | Plant Nutrition    
Segment Reporting Information [Line Items]    
Sales to external customers 60.8 61.4
Operating Segments | Highway Deicing Salt | Salt    
Segment Reporting Information [Line Items]    
Sales to external customers 210.8 138.1
Operating Segments | Highway Deicing Salt | Plant Nutrition    
Segment Reporting Information [Line Items]    
Sales to external customers 0.0 0.0
Operating Segments | Consumer & Industrial Salt | Salt    
Segment Reporting Information [Line Items]    
Sales to external customers 120.7 104.1
Operating Segments | Consumer & Industrial Salt | Plant Nutrition    
Segment Reporting Information [Line Items]    
Sales to external customers 0.0 0.0
Operating Segments | SOP | Salt    
Segment Reporting Information [Line Items]    
Sales to external customers 0.0 0.0
Operating Segments | SOP | Plant Nutrition    
Segment Reporting Information [Line Items]    
Sales to external customers 61.8 64.6
Operating Segments | Eliminations & Other | Salt    
Segment Reporting Information [Line Items]    
Sales to external customers 0.0 0.0
Operating Segments | Eliminations & Other | Plant Nutrition    
Segment Reporting Information [Line Items]    
Sales to external customers (1.0) (3.2)
Corporate & Other    
Segment Reporting Information [Line Items]    
Sales to external customers 3.8 3.6
Corporate & Other | Highway Deicing Salt    
Segment Reporting Information [Line Items]    
Sales to external customers 0.0 0.0
Corporate & Other | Consumer & Industrial Salt    
Segment Reporting Information [Line Items]    
Sales to external customers 0.0 0.0
Corporate & Other | SOP    
Segment Reporting Information [Line Items]    
Sales to external customers 0.0 0.0
Corporate & Other | Eliminations & Other    
Segment Reporting Information [Line Items]    
Sales to external customers $ 3.8 $ 3.6
v3.25.4
STOCKHOLDERS’ EQUITY AND EQUITY INSTRUMENTS - Narrative (Details)
$ in Millions
 3 Months Ended
Dec. 31, 2025
USD ($)
wk
shares
Dec. 31, 2024
USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of weeks for grant | wk 50  
Selling, General and Administrative Expenses    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based payment arrangement, expense | $ $ 2.3 $ 3.9
Equity Awards    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based payment arrangement, nonvested award, option, cost not yet recognized, amount | $ $ 13.5  
Share-based payment arrangement, nonvested award, cost not yet recognized, period for recognition 1 year 10 months 24 days  
RSUs    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based compensation arrangement by share-based payment award, non-option equity instruments, granted (in shares) 446,396  
Number of shares available from conversion (in shares) 1  
RSUs | Director    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based compensation arrangement by share-based payment award, non-option equity instruments, granted (in shares) 5,392  
RSUs | Minimum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Performance period 1 year  
RSUs | Maximum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Performance period 3 years  
Stock Payments    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Reissued share of treasury stock (in shares) 6,641  
Deferred Stock Unit    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based compensation arrangement by share-based payment award, non-option equity instruments, granted (in shares) 2,260  
Scorecard PSUs    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based compensation arrangement by share-based payment award, non-option equity instruments, granted (in shares) 182,071  
Performance period 3 years  
Modifier change 20.00%  
Dividend yield (as a percent) 0.00%  
Scorecard PSUs | Minimum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based compensation payment award performance percentage 0.00%  
Expected volatility (as a percent) 48.00%  
Risk-free rate of return (as a percent) 3.50%  
Scorecard PSUs | Maximum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based compensation payment award performance percentage 200.00%  
Stock Options    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Performance period 4 years  
Number of shares available from conversion (in shares) 1  
Award expiration period 7 years  
v3.25.4
STOCKHOLDERS’ EQUITY AND EQUITY INSTRUMENTS - Schedule of Stock-Based Compensation Activity (Details)
$ / shares in Units, $ in Millions
 3 Months Ended
Dec. 31, 2025
USD ($)
$ / shares
shares
Stock Options  
Number  
Outstanding at beginning of period (in shares) 107,261
Granted (in shares) 0
Released from restriction (in shares) 0
Cancelled/expired (in shares) (794)
Outstanding at end of period (in shares) 106,467
Weighted-average exercise price  
Weighted-average exercise price at beginning of period (in dollars per share) | $ / shares $ 63.43
Weighted-average exercise price, granted (in dollars per share) | $ / shares 0
Weighted-average exercise price, released from restriction (in dollars per share) | $ / shares 0
Weighted-average exercise price, cancelled/expired (in dollars per share) | $ / shares 67.50
Weighted-average exercise price at end of period (in dollars per share) | $ / shares $ 63.40
RSUs  
Number  
Outstanding at beginning of period (in shares) 828,922
Granted (in shares) 446,396
Released from restriction (in shares) (185,719)
Cancelled/expired (in shares) (781)
Outstanding at end of period (in shares) 1,088,818
Weighted-average fair value  
Weighted-average fair value at beginning of period (in dollars per share) | $ / shares $ 15.34
Weighted-average fair value, granted (in dollars per share) | $ / shares 17.83
Weighted-average fair value, released from restriction (in dollars per share) | $ / shares 17.07
Weighted-average fair value, cancelled/expired (in dollars per share) | $ / shares 15.85
Weighted-average fair value at end of period (in dollars per share) | $ / shares $ 16.11
PSUs  
Number  
Outstanding at beginning of period (in shares) 316,480
Granted (in shares) 182,071
Released from restriction (in shares) 0
Cancelled/expired (in shares) 0
Outstanding at end of period (in shares) 498,551
Weighted-average fair value  
Weighted-average fair value at beginning of period (in dollars per share) | $ / shares $ 16.89
Weighted-average fair value, granted (in dollars per share) | $ / shares 19.37
Weighted-average fair value, released from restriction (in dollars per share) | $ / shares 0
Weighted-average fair value, cancelled/expired (in dollars per share) | $ / shares 0
Weighted-average fair value at end of period (in dollars per share) | $ / shares $ 17.22
PSU at grant date (in shares per unit) 1
Equity Awards  
Weighted-average fair value  
Fair value of stock withheld related to vesting of RSUs and PSUs | $ $ 1.2
v3.25.4
STOCKHOLDERS’ EQUITY AND EQUITY INSTRUMENTS - Schedule of Components and Changes in Accumulated Other Comprehensive Income (Loss) (Details)
$ in Millions
 3 Months Ended
Dec. 31, 2025
USD ($)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]  
Beginning Balance $ 234.1
Other comprehensive loss before reclassifications 6.0
Amounts reclassified from AOCL 0.7
Net current period other comprehensive income (loss) 6.7
Ending Balance 260.5
Loss on foreign exchange of intercompany notes of long-term nature 1.4
Total  
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]  
Beginning Balance (107.9)
Ending Balance (101.2)
Gains and (Losses) on Cash Flow Hedges  
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]  
Beginning Balance (0.8)
Other comprehensive loss before reclassifications (1.0)
Amounts reclassified from AOCL 0.5
Net current period other comprehensive income (loss) (0.5)
Ending Balance (1.3)
Benefit Plans | Defined Benefit Pension  
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]  
Beginning Balance (6.3)
Other comprehensive loss before reclassifications 0.0
Amounts reclassified from AOCL 0.2
Net current period other comprehensive income (loss) 0.2
Ending Balance (6.1)
Benefit Plans | Other Post-Employment Benefits  
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]  
Beginning Balance 1.8
Other comprehensive loss before reclassifications 0.0
Amounts reclassified from AOCL 0.0
Net current period other comprehensive income (loss) 0.0
Ending Balance 1.8
Foreign Currency  
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]  
Beginning Balance (102.6)
Other comprehensive loss before reclassifications 7.0
Amounts reclassified from AOCL 0.0
Net current period other comprehensive income (loss) 7.0
Ending Balance $ (95.6)
v3.25.4
DERIVATIVE FINANCIAL INSTRUMENTS - Narrative (Details)
MMBTU in Millions, $ in Millions
 3 Months Ended 6 Months Ended
Dec. 31, 2025
USD ($)
MMBTU
Dec. 31, 2024
USD ($)
Mar. 31, 2025
MMBTU
Derivatives, Fair Value [Line Items]      
Net gains to be reclassified from accumulated other comprehensive loss to earnings during the next 12 months $ 1.3    
Commodity Contract      
Derivatives, Fair Value [Line Items]      
Notional amount (in MMBtus) | MMBTU 2.0   2.6
Commodity Contract | Derivatives Designated as Hedging Instruments      
Derivatives, Fair Value [Line Items]      
Percent of forecasted usage to be hedged 90.00%    
Maximum period which the company hedges in advance of forecasted purchase 36 months    
Natural Gas Instruments, Net | Derivatives Designated as Hedging Instruments | Cash Flow Hedging      
Derivatives, Fair Value [Line Items]      
Net cash expense in product cost $ 0.5 $ 0.6  
v3.25.4
DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Fair Value of Derivatives (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Sep. 30, 2025
Derivatives, Fair Value [Line Items]    
Asset Derivatives $ 5.4 $ 7.9
Liability Derivatives 6.7 8.7
Commodity Contract    
Derivatives, Fair Value [Line Items]    
Netting of contracts in a receivable position against contracts in payable position 5.3 7.8
Commodity Contract | Derivatives Designated as Hedging Instruments | Other current assets    
Derivatives, Fair Value [Line Items]    
Asset Derivatives 5.3 6.2
Commodity Contract | Derivatives Designated as Hedging Instruments | Accrued expenses and other current liabilities    
Derivatives, Fair Value [Line Items]    
Liability Derivatives 6.6 7.1
Commodity Contract | Derivatives Designated as Hedging Instruments | Other assets    
Derivatives, Fair Value [Line Items]    
Asset Derivatives 0.1 1.7
Commodity Contract | Derivatives Designated as Hedging Instruments | Other noncurrent liabilities    
Derivatives, Fair Value [Line Items]    
Liability Derivatives $ 0.1 $ 1.6
v3.25.4
DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Activity Related to Other Accumulated Comprehensive (Loss) Income Before Taxes (Details) - Cash Flow Hedging
$ in Millions
 3 Months Ended
Dec. 31, 2025
USD ($)
Derivative Instruments, Gain (Loss) [Line Items]  
Net Loss Recognized in AOCL on Derivatives (Effective Portion) $ (1.0)
Net Loss Reclassified from AOCL into Income (Effective Portion) 0.5
Commodity Contract | Cost of Sales  
Derivative Instruments, Gain (Loss) [Line Items]  
Net Loss Recognized in AOCL on Derivatives (Effective Portion) (1.0)
Net Loss Reclassified from AOCL into Income (Effective Portion) $ 0.5
v3.25.4
FAIR VALUE MEASUREMENTS - Schedule of Estimated Fair Values for Type of Instrument (Details)
$ in Millions
 3 Months Ended
Dec. 31, 2025
USD ($)
Asset Class:  
Mutual fund investments in a non-qualified savings plan $ 3.7
Total assets at fair value 9.1
Liability Class:  
Liabilities related to non-qualified savings plan 3.7
Total liabilities at fair value $ 10.4
Common Stock, Large Cap US Companies | Mutual Fund Investments, Concentration Risk | Investment Benchmark  
Liability Class:  
Investment concentration risk (as a percent) 32.00%
Common Stock of Small to Mid Cap US Companies | Mutual Fund Investments, Concentration Risk | Investment Benchmark  
Liability Class:  
Investment concentration risk (as a percent) 4.00%
Common Stock, International Companies | Mutual Fund Investments, Concentration Risk | Investment Benchmark  
Liability Class:  
Investment concentration risk (as a percent) 3.00%
Bond Funds | Mutual Fund Investments, Concentration Risk | Investment Benchmark  
Liability Class:  
Investment concentration risk (as a percent) 10.00%
Short-Term Investments | Mutual Fund Investments, Concentration Risk | Investment Benchmark  
Liability Class:  
Investment concentration risk (as a percent) 16.00%
Blended Funds | Mutual Fund Investments, Concentration Risk | Investment Benchmark  
Liability Class:  
Investment concentration risk (as a percent) 35.00%
Derivatives Designated as Hedging Instruments  
Asset Class:  
Derivatives – natural gas instruments, net $ 5.4
Liability Class:  
Derivatives - natural gas instruments, net 6.7
Quoted Prices in Active Market (Level One)  
Asset Class:  
Mutual fund investments in a non-qualified savings plan 3.7
Total assets at fair value 3.7
Liability Class:  
Liabilities related to non-qualified savings plan 3.7
Total liabilities at fair value 3.7
Quoted Prices in Active Market (Level One) | Derivatives Designated as Hedging Instruments  
Asset Class:  
Derivatives – natural gas instruments, net 0.0
Liability Class:  
Derivatives - natural gas instruments, net 0.0
Significant Other Observable Inputs (Level Two)  
Asset Class:  
Mutual fund investments in a non-qualified savings plan 0.0
Total assets at fair value 5.4
Liability Class:  
Liabilities related to non-qualified savings plan 0.0
Total liabilities at fair value 6.7
Significant Other Observable Inputs (Level Two) | Derivatives Designated as Hedging Instruments  
Asset Class:  
Derivatives – natural gas instruments, net 5.4
Liability Class:  
Derivatives - natural gas instruments, net 6.7
Significant Unobservable Inputs (Level Three)  
Asset Class:  
Mutual fund investments in a non-qualified savings plan 0.0
Total assets at fair value 0.0
Liability Class:  
Liabilities related to non-qualified savings plan 0.0
Total liabilities at fair value 0.0
Significant Unobservable Inputs (Level Three) | Derivatives Designated as Hedging Instruments  
Asset Class:  
Derivatives – natural gas instruments, net 0.0
Liability Class:  
Derivatives - natural gas instruments, net $ 0.0
v3.25.4
FAIR VALUE MEASUREMENTS - Schedule of Fair value in the Statement of Financial Position (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Jun. 16, 2025
Nov. 30, 2019
0.08 Senior Notes due July 2030      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Debt fair value amount $ 650.0    
0.08 Senior Notes due July 2030 | Quoted Prices in Active Market (Level One)      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Debt fair value amount 0.0    
0.08 Senior Notes due July 2030 | Significant Other Observable Inputs (Level Two)      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Debt fair value amount 679.3    
0.08 Senior Notes due July 2030 | Significant Unobservable Inputs (Level Three)      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Debt fair value amount $ 0.0    
0.08 Senior Notes due July 2030 | Senior Notes      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Stated interest rate 8.00% 8.00%  
6.75% Senior Notes due December 2027      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Debt fair value amount $ 150.0    
6.75% Senior Notes due December 2027 | Quoted Prices in Active Market (Level One)      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Debt fair value amount 0.0    
6.75% Senior Notes due December 2027 | Significant Other Observable Inputs (Level Two)      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Debt fair value amount 149.5    
6.75% Senior Notes due December 2027 | Significant Unobservable Inputs (Level Three)      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Debt fair value amount $ 0.0    
6.75% Senior Notes due December 2027 | Senior Notes      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Stated interest rate 6.75%   6.75%
v3.25.4
NET INCOME (LOSS) PER SHARE (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Millions
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Numerator:    
Net income (loss) $ 18.6 $ (23.6)
Less: net income allocated to participating securities (0.3) 0.0
Net income (loss) available to common stockholders, basic 18.3 (23.6)
Net income (loss) available to common stockholders, diluted $ 18.3 $ (23.6)
Denominator (in thousands):    
Weighted-average common shares outstanding for basic net income (loss) per share (in shares) 42,083 41,441
Weighted-average effect of dilutive equity awards outstanding (in shares) 184 0
Shares for diluted net income (loss) per share (in shares) 42,267 41,441
Basic net income (loss) per common share (in dollars per share) $ 0.43 $ (0.57)
Diluted net income (loss) per common share (in dollars per share) $ 0.43 $ (0.57)
Net income was allocated to weighted participating securities 693,000 1,116,000
Stock Options    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive weighted options outstanding (in shares) 670,000 1,184,000
v3.25.4
RELATED PARTY TRANSACTIONS (Details) - USD ($)
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Sep. 30, 2025
Related Party Transaction [Line Items]      
Total revenues $ 396,100,000 $ 307,200,000  
Total receivables 278,600,000   $ 179,600,000
Accounts payable 100,600,000   $ 96,000,000.0
Purchased of salt-treatment materials 1,100,000    
Koch, Inc.      
Related Party Transaction [Line Items]      
Total revenues 500,000 1,100,000  
Total receivables 200,000    
Accounts payable 0 $ 0  
Related Party      
Related Party Transaction [Line Items]      
Accounts payable $ 300,000    
v3.25.4
Subsequent Events (Details)
$ in Millions
Feb. 02, 2026
USD ($)
Subsequent Event | SOP Facility | Disposal Group, Disposed of by Sale, Not Discontinued Operations  
Subsequent Event [Line Items]  
Gross proceeds received $ 30.8