STOCK-BASED COMPENSATION (Details 2)	9 Months Ended
Sep. 30, 2021 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Share Award, Total Shareholder Return Percent	50.00%
Performance Share Award Cycle	3
Performance Share Award, Net Income Percent	50.00%
Black-Sholes Option-Pricing Model
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	2.76%
Risk-free interest rate	0.94%
Expected volatility of Olin common stock	44.00%
Expected life (years)	7 years
Weighted-average grant fair value (per option) \| $ / shares	$ 9.91
Weighted-average exercise price \| $ / shares	$ 28.99
Options granted \| shares	1,094,700
Monte Carlo Simulation Model
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.23%
Expected volatility of Olin common stock	55.00%
Expected life (years)	3 years
Expected average volatility of peer companies	0.50
Average correlation coefficient of peer companies	0.50
Grant date fair value (TSR based award) \| $	$ 39.96
Grant date fair value (net income based award) \| $	$ 28.99
Awards granted \| shares	248,700

The term (in years) of performance share awards.

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The grant date fair value of the net income portion of the performance share award.

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Percent of performance share awards that is based on net income.

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The grant date fair value of the total shareholder return portion of the performance share award.

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Percent of performance share awards that is based on total shareholder return.

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Net number of performance share awards granted during the period.

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Share Based Compensation Arrangements Expected Volatility Rate of Peer Companies

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Share Based Compensation Average Correlation Coefficient of Peer Companies

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Net number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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