SUPPLEMENTAL GUARANTOR FINANCIAL INFORMATION (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Oct. 05, 2015
2023 Notes
Business Acquisition [Line Items]
2023 Senior Notes			$ 720.0
Interest rate	9.75%	9.75%	9.75%
2025 Notes
Business Acquisition [Line Items]
Interest rate	10.00%	10.00%	10.00%
2025 Senior Notes			$ 500.0

9.75% senior notes due 2023 that were issued on the Closing Date of the Transactions.

No definition available.

Name:	oln_A2023SeniorNotes
Namespace Prefix:	oln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

10.00% senior notes due 2025 that were issued on the Closing Date of the Transactions.

+ References

No definition available.

+ Details

Name:	oln_A2025SeniorNotes
Namespace Prefix:	oln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=oln_A2023NotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=oln_A2025NotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: