DEBT (Details 1) - USD ($) $ in Millions	9 Months Ended
DEBT (Details 1) - USD ($) $ in Millions	Sep. 30, 2025	Mar. 14, 2025	Dec. 31, 2024	Nov. 20, 2024	Sep. 30, 2024
Debt Instrument [Line Items]
Receivables Financing Agreements	$ 470.0		$ 475.0		$ 339.8
Deferred debt issuance costs	(19.0)		(14.3)		(14.0)
Unamortized bond original issue discount	0.0		(0.1)		(0.1)
Total debt	2,993.4		2,842.2		2,889.5
Amounts due within one year	19.2		129.0		123.9
Total long-term debt	2,974.2		2,713.2		2,765.6
Quarterly Required Principal Payment Percent Through 2027		0.625%
Quarterly Required Principal Payment Percent After 2027		1.25%
Interest and Debt Expense	3.3
AR Facilities, Recourse Liability	0.0		0.0		0.0
9.5% senior note
Debt Instrument [Line Items]
Notes Payable	$ 0.0		$ 108.6		$ 108.6
Debt Instrument, Interest Rate, Stated Percentage	9.50%		9.50%		9.50%
5.125% senior note
Debt Instrument [Line Items]
Notes Payable	$ 0.0		$ 500.0		$ 500.0
Debt Instrument, Interest Rate, Stated Percentage	5.125%		5.125%		5.125%
5.625% senior note
Debt Instrument [Line Items]
Notes Payable	$ 669.3		$ 669.3		$ 669.3
Debt Instrument, Interest Rate, Stated Percentage	5.625%		5.625%		5.625%
5.00% senior note
Debt Instrument [Line Items]
Notes Payable	$ 515.3		$ 515.3		$ 515.3
Debt Instrument, Interest Rate, Stated Percentage	5.00%		5.00%		5.00%
6.625% senior note
Debt Instrument [Line Items]
Notes Payable	$ 600.0		$ 0.0		$ 0.0
Debt Instrument, Interest Rate, Stated Percentage	6.625%		6.63%		6.63%
Variable-rate Term Loan [Member]
Debt Instrument [Line Items]
Notes Payable	$ 641.9		$ 332.5		$ 334.7
Variable-rate Senior Revolving Facility
Debt Instrument [Line Items]
Notes Payable	30.0		170.0		350.0
Variable-rate Recovery Zone bonds
Debt Instrument [Line Items]
Notes Payable	83.0		83.0		83.0
Variable-rate industrial and environmental obligations
Debt Instrument [Line Items]
Notes Payable	2.9		2.9		2.9
$1,850.0 Million Secured Credit Facility
Debt Instrument [Line Items]
2025 Senior Credit Facility		$ 1,850.0
2025 Senior Credit Facility Increase		300.0
Senior Term Loan
Debt Instrument [Line Items]
Notes Payable		350.0
9.5% senior note before paydown
Debt Instrument [Line Items]
Notes Payable	108.6
5.125% senior note before paydown
Debt Instrument [Line Items]
Notes Payable	500.0
2022 Senior Term Loan
Debt Instrument [Line Items]
Notes Payable		$ 332.5
Receivables Financing Agreement
Debt Instrument [Line Items]
Receivables Financing Agreements			$ 475.0		$ 339.8
Secured Borrowing Maximum Capacity				$ 500.0
Secured Borrowing Maximum Capacity Borrowing Limit				425.0
Secured Borrowing Maximum Capacity Increase				$ 75.0
Trade Receivables Pledged as Collateral for Secured Borrowings	617.0
Receivables Financing Agreement Available Borrowing Capacity	$ 28.0

OLIN Corp 10-Q