STOCK-BASED COMPENSATION (Details 4)	Dec. 31, 2019 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sub-limit for all types of stock awards included in available to be issued stock options (in shares)	1,589,950
2000 long term incentive plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved for Issuance (in shares)	42,130
Number of shares available for grant or purchase (in shares)	0
2003 long term incentive plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved for Issuance (in shares)	187,184
Number of shares available for grant or purchase (in shares)	0
2006 long term incentive plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved for Issuance (in shares)	164,138
Number of shares available for grant or purchase (in shares)	0
2009 long term incentive plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved for Issuance (in shares)	1,701,404
Number of shares available for grant or purchase (in shares)	0
2014 long term incentive plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved for Issuance (in shares)	1,821,795
Number of shares available for grant or purchase (in shares)	0
2016 long term incentive plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved for Issuance (in shares)	2,285,000
Number of shares available for grant or purchase (in shares)	0
2018 long term incentive plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved for Issuance (in shares)	9,583,249
Number of shares available for grant or purchase (in shares)	7,646,099
Long Term Incentive Stock Option Plan Reserved for Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved for Issuance (in shares)	15,784,900
Long Term Incentive Stock Option Plan Available for Grant or Purchase
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant or purchase (in shares)	7,646,099
1997 stock plan for non-employee directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved for Issuance (in shares)	483,860
Number of shares available for grant or purchase (in shares)	302,796

Sub-limit for all types of stock awards included in available to be issued stock options.

No definition available.

Name:	oln_SubLimitForAllTypesOfStockAwardsIncludedInAvailableToBeIssuedStockOptions
Namespace Prefix:	oln_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares authorized for issuance under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_PlanNameAxis=oln_LongTermIncentivePlan2000Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=oln_LongTermIncentivePlan2003Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=oln_LongTermIncentivePlan2006Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=oln_LongTermIncentivePlan2009Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=oln_LongTermIncentivePlan2014Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=oln_LongTermIncentivePlan2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=oln_LongTermIncentivePlan2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=oln_LongTermIncentiveStockOptionPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=oln_LongTermIncentiveStockOptionPlanExpiredAndAssumedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=oln_StockPlanForNonEmployeeDirectors1997Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: