SHAREHOLDERS' EQUITY (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 11, 2024	Jul. 28, 2022
Equity, Class of Treasury Stock [Line Items]
Cost of common stock repurchased and retired	$ 50.5	$ 300.3	$ 711.3
Stock options exercised (in shares)	0.1	0.9	1.0
Total value of stock options exercised	$ 2.3	$ 23.9	$ 25.4
Foreign currency translation adjustment [Roll Forward]
Beginning balance	(45.9)	(39.7)	(38.6)
Unrealized (losses) gains	(6.3)	(6.2)	(1.1)
Reclassification adjustments of (gains) losses into income	0.0	0.0	0.0
Tax benefit (provision)	0.0	0.0	0.0
Net change	(6.3)	(6.2)	(1.1)
Ending balance	(52.2)	(45.9)	(39.7)
Unrealized gains (losses) on derivative contracts (net of taxes) [Roll Forward]
Beginning balance	7.8	(18.4)	(32.5)
Unrealized (losses) gains	14.2	4.3	(53.6)
Reclassification adjustments of (gains) losses into income	(16.6)	30.6	72.5
Tax benefit (provision)	0.5	(8.7)	(4.8)
Net change	(1.9)	26.2	14.1
Ending balance	5.9	7.8	(18.4)
Pension and postretirement benefits (net of taxes) [Roll Forward]
Beginning balance	(412.0)	(438.2)	(424.8)
Unrealized (losses) gains	52.1	29.7	(18.1)
Reclassification adjustments of (gains) losses into income	5.6	6.2	0.2
Tax benefit (provision)	(13.9)	(9.7)	4.5
Net change	43.8	26.2	(13.4)
Ending balance	(368.2)	(412.0)	(438.2)
Accumulated other comprehensive loss [Roll Forward]
Beginning balance	(450.1)	(496.3)	(495.9)
Unrealized (losses) gains	60.0	27.8	(72.8)
Reclassification adjustments of (gains) losses into income	(11.0)	36.8	72.7
Tax benefit (provision)	(13.4)	(18.4)	(0.3)
Net change	35.6	46.2	(0.4)
Ending balance	$ (414.5)	$ (450.1)	$ (496.3)
Common Stock
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Shares	2.2	5.9	13.3
Cost of common stock repurchased and retired	$ 50.5	$ 300.3	$ 711.3
Common Stock \| 2024 Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Authorized share repurchase program (in dollars)				$ 1,300.0
Stock Repurchased and Retired During Period, Shares	0.0
Common Stock \| 2022 Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Authorized share repurchase program (in dollars)					$ 2,000.0
Stock Repurchased and Retired During Period, Shares	27.4
Cost of common stock repurchased and retired	$ 1,351.1
Remaining authorized repurchase amount (in dollars)	$ 648.9

OLIN Corp 10-K