CONTRIBUTING EMPLOYEE OWNERSHIP PLAN (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CONTRIBUTING EMPLOYEE OWNERSHIP PLAN [Abstract]
Employer matching contributions to employee ownership plan	$ 5.2	$ 2.0	$ 5.0
Initial vesting period (in years)	two
Initial vesting period vested percentage	25.00%
Additional vesting percentage for each additional year of service	25.00%
Years of service for full vesting	five
Vesting percentage after five years	100.00%
Number of days an employee is prohibited from trading out of the fund to which the transfer was made	seven

Additional vesting percentage for each year of service, after the initial two years of service.

No definition available.

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Namespace Prefix:	oln_
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Period Type:	duration

- Definition

Minimum term of service before an employee becomes vested in the plan.

+ References

No definition available.

+ Details

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Namespace Prefix:	oln_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Initial vesting percentage after an employee completes two years of service.

+ References

No definition available.

+ Details

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Namespace Prefix:	oln_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of days employees are prohibited from trading out of the fund to which the transfer was made.

+ References

No definition available.

+ Details

Name:	oln_ContributingEmployeeOwnershipPlanNumberOfDaysEmployeeIsProhibitedFromTradingOutOfFundToWhichTransferWasMade
Namespace Prefix:	oln_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Vesting percentage after an employee serves five years.

+ References

No definition available.

+ Details

Name:	oln_ContributingEmployeeOwnershipPlanVestingPercentageAfterFiveYears
Namespace Prefix:	oln_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of years an employee serves before full vesting in the plan.

+ References

No definition available.

+ Details

Name:	oln_ContributingEmployeeOwnershipPlanYearsOfServiceForFullVesting
Namespace Prefix:	oln_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 11

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration