EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Earnings Per Share [Abstract]
Net income	$ 144.7	$ 422.1	$ 298.7	$ 815.1
Net loss attributable to noncontrolling interests	(2.2)	0.0	(4.5)	0.0
Net income attributable to Olin Corporation	$ 146.9	$ 422.1	$ 303.2	$ 815.1
Basic shares	127.4	149.2	129.2	151.9
Basic net income attributable to Olin Corporation per share	$ 1.15	$ 2.83	$ 2.35	$ 5.37
Earnings Per Share, Diluted [Abstract]
Basic shares	127.4	149.2	129.2	151.9
Stock-based compensation	3.0	3.6	3.2	3.7
Diluted shares	130.4	152.8	132.4	155.6
Diluted net income attributable to Olin Corporation per share	$ 1.13	$ 2.76	$ 2.29	$ 5.24
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	1.3	0.8	1.3	0.8