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Cash remitted to PolyOne for distributable cash generated by SunBelt.

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Additional accretion expense for the earn out liability that was recorded as a result of the acquisition included in pro forma results.

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SunBelt pretax income included in Chlor Alkali Products.

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The total fair value of net assets and liabilities acquired, before allocation of goodwill.

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Discrete deferred tax expense relating to the SunBelt acquisition.

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Percent of distributable cash generated by non-consolidated affiliate.

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Time term for earn out agreement.

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This item represents the entity's proportionate share of SunBelt's earnings for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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Membrane technology capacity of plant.

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Ownership percentage of target after acquisition.

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Pro forma increase of tax provision due to fair value adjustments included in pro forma results.

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Reduction of depreciation expense related to the fair value adjustment to property, plant and equipment included in pro forma results

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Reduction in interest expense as a result of increasing the carrying value of acquired debt obligations to its estimated fair value included in pro forma results.

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Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition.

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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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Percentage of voting equity interests acquired in the business combination.

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The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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The amount of acquisition cost of a business combination allocated to assets acquired.

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The amount of cash and cash equivalents acquired in a business combination.

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The amount of acquisition cost of a business combination allocated to current liabilities of the acquired entity.

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The amount of acquisition cost of a business combination allocated to the current portion of long-term debt of the acquired entity.

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Amount of deferred tax assets or liabilities for the differences between the values assigned and the tax bases of assets and liabilities in a business combination, net of any valuation allowance for deferred tax assets.

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Amount of goodwill arising from a business combination, which is the excess of the cost of the acquired entity over the amounts assigned to assets acquired and liabilities assumed.

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The amount of goodwill arising from a business combination that is expected to be deductible for tax purposes.

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The amount of acquisition cost of a business combination allocated to liabilities assumed.

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The amount of acquisition cost of a business combination allocated to the noncurrent portion of the long-term debt assumed from the acquired entity.

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The amount of acquisition cost of a business combination allocated to noncurrent assets of the acquired entity, except for property plant and equipment, intangible assets, and goodwill.

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The amount of acquisition cost of a business combination allocated to other noncurrent liabilities of the acquired entity.

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The amount of acquisition cost of a business combination allocated to property, plant and equipment to be used in ongoing operations.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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The amount, measured at acquisition-date fair value, of all liabilities assumed that arise from contingencies and were recognized by the entity.

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This element represents the amount of earnings or loss of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

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In a business combination achieved in stages, this element represents the acquisition-date percentage of equity in the acquiree held by the acquirer immediately before the acquisition date.

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ACQUISITION (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended		1 Months Ended	3 Months Ended	12 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended		12 Months Ended
	Feb. 28, 2011	Sep. 30, 2011	Feb. 28, 2011 SunBelt [Member]	Jun. 30, 2011 SunBelt [Member]	Dec. 31, 2011 SunBelt [Member]	Mar. 31, 2011 SunBelt [Member]	Sep. 30, 2011 SunBelt [Member]	Sep. 30, 2010 SunBelt [Member]	Sep. 30, 2011 SunBelt [Member]	Sep. 30, 2010 SunBelt [Member]	Dec. 31, 2011 Guaranteed Senior Secured Notes due 2017, Series O [Member]	Dec. 22, 1997 Guaranteed Senior Secured Notes due 2017, Series O [Member]	Dec. 31, 2011 Guaranteed Senior Secured Notes due 2017, Series G [Member]	Dec. 22, 1997 Guaranteed Senior Secured Notes due 2017, Series G [Member]
Business Acquisition [Line Items]
PolyOne Corporation's interest in SunBelt (in hundredths)		50.00%	50.00%
Cash consideration for SunBelt purchase			$ 132.3
Olin's ownership percentage of SunBelt after acquisition of PolyOne's interest (in hundredths)			100.00%
Membrane technology capacity of plant			350,000
Earn out agreement term			three year
Cash remitted to PolyOne for distributable cash generated by SunBelt				6.0
Distributable cash non-consolidated affiliate				50.00%
Required annual debt repayment for Series O and Series G notes					12.2						6.1		6.1
Remaining principal balance of consolidated notes			85.3
Previous equity percentage in SunBelt (in hundredths)		50.00%	50.00%
Discrete deferred tax expense relating to the SunBelt acquisition			76.0
Total current assets			37.6
Property, plant and equipment			87.4
Deferred income taxes			0.4
Other assets			5.8
Total assets acquired			131.2
Total current liabilities			42.7
Long-term debt			75.1
Other liabilities			27.6
Total liabilities assumed			145.4
Less Investment in SunBelt			(0.8)
Net liabilities assumed			(13.4)
Liabilities for uncertainties			48.3
Gain on remeasurement of investment in SunBelt			181.4
Goodwill			327.1			327.9
Fair value of assets acquired			180.6
Cash and cash equivalents			8.9
Current installment of long term debt			12.2
Equity earnings of nonconsolidated affiliate for Sunbelt			6.3
Pretax gain on acquisition of SunBelt			181.4
Debt Instrument [Line Items]
Face amount of senior secured notes												97.5		97.5
Interest rate on SunBelt notes												7.23%		7.23%
Required annual debt repayment for Series O and Series G notes					12.2						6.1		6.1
Finite-Lived Intangible Assets [Line Items]
Final valuation of intangible assets relating to customers, customer contracts and relationships	5.8
Estimated useful life of intangible assets (in years)	15
Tax deductible portion of goodwill	163.7
Segment Reporting Information [Line Items]
SunBelt sales							58.9		125.0
SunBelt pretax income							11.7		23.2
SunBelt pretax income included in Chlor Alkali Products							14.4		29.4
Sunbelt acquisition costs included in Chlor Alkali Products									0.8
Sunbelt interest expense							1.0		2.8
Pro forma summary of the condensed statements of income as if the Sunbelt acquisition occurred on January 1, 2010 [Abstract]
Sales								484.4	1,541.6	1,321.1
Net income								44.9	121.9	86.4
Net income per common share basic (in dollars per share)								$ 0.57	$ 1.53	$ 1.09
Net income per common share diluted (in dollars per share)								$ 0.56	$ 1.51	$ 1.08
Additional amortization expense related to the fair value of acquired identifiable intangible assets								0.1	0.1	0.3
Reduction of depreciation expense related to the fair value adjustment to property, plant and equipment								1.4	1.0	4.3
Reduction in interest expense as a result of increasing the carrying value of acquired debt obligations to its estimated fair value								0.2	0.1	0.4
Additional accretion expense for the earn out liability that was recorded as a result of the acquisition								0.6	0.4	1.9
Deferred tax expense related to the tax effect of gain on the remeasurement of equity interest in SunBelt									76.0
Pro forma increase of tax provision due to fair value adjustments								3.4	2.3	6.1
Expense for earn out liability							$ 1.7		$ 2.6