This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. The element may be used in both the balance sheet and disclosure in the same submission. A forward contract or is a non-standardized contract between two parties to buy or sell an asset at a specified future time at a price agreed today.

Name:	oln_CommodityForwardContractsAssetFairValueDisclosure
Namespace Prefix:	oln
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

FAIR VALUE MEASUREMENTS (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended												6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Feb. 28, 2011	Jun. 30, 2011 Fair Value Measurements Level 1 [Member]	Dec. 31, 2010 Fair Value Measurements Level 1 [Member]	Jun. 30, 2010 Fair Value Measurements Level 1 [Member]	Jun. 30, 2011 Fair Value Measurements Level 2 [Member]	Dec. 31, 2010 Fair Value Measurements Level 2 [Member]	Jun. 30, 2010 Fair Value Measurements Level 2 [Member]	Jun. 30, 2011 Fair Value Measurements Level 3 [Member]	Dec. 31, 2010 Fair Value Measurements Level 3 [Member]	Jun. 30, 2010 Fair Value Measurements Level 3 [Member]	Jun. 30, 2011 Financial Instruments [Member]	Jun. 30, 2010 Financial Instruments [Member]	Jun. 30, 2011 Long term Debt Fair Value Disclosure [Member]	Dec. 31, 2010 Long term Debt Fair Value Disclosure [Member]	Jun. 30, 2010 Long term Debt Fair Value Disclosure [Member]	Jun. 30, 2011 Long Term Debt Carrying Amount [Member]	Dec. 31, 2010 Long Term Debt Carrying Amount [Member]	Jun. 30, 2010 Long Term Debt Carrying Amount [Member]
Assets
Interest rate swaps				$ 0	$ 0	$ 0	$ 8.4	$ 9.1	$ 11.4	$ 0	$ 0	$ 0
Commodity forward contracts				3.3	7.0	0	5.3	9.9	0.2	0	0	0
Liabilities
Interest rate swaps				0	0	0	8.5	9.3	12.0	0	0	0
Earn out				0			0			43.2
Foreign currency contracts						0.3			0			0
Commodity forward contracts				0	0	1.4	0.1	0.2	0.3	0	0	0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of year													0	0
Unrealized loss included in other income													(0.9)	0
Purchases, sales and settlements													(42.3)	0
Balance at end of period													(43.2)	0
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated fair value of debt															613.1	530.3	414.9	582.8	496.0	402.3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Assets measured at fair value on a nonrecurring basis			180.6
Gain on acquisition of Sunbelt	$ 181.4	$ 0
PolyOne's interest in Sunbelt	50.00%