Acquisitions (Purchase Consideration Transferred) (Details) (Vinnolit [Member], USD $) In Thousands, unless otherwise specified	0 Months Ended
	Jul. 31, 2014		Jul. 31, 2014
Business Acquisition [Line Items]
Cash paid to Sellers	$ 309,619
Cash deposited in escrow	13,390	[1]
Retirement of long-term debt as of July 31, 2014, on behalf of the Sellers	413,215	[2]
Total purchase consideration	736,224
Assets:
Cash			125,137
Working capital, excluding inventory and cash			23,072	[3]
Inventories			114,961	[4]
Property, plant and equipment			471,123
Investments			51,552
Other assets			65,366	[5]
Intangible assets:
Deferred income tax asset - current			8,697
Deferred income tax asset - non-current			27,387
Liabilities:
Pension obligation			(117,970)
Other long-term liabilities			(10,723)
Power purchase agreement liability			(10,826)	[6]
Deferred income tax liability - current			(6,845)
Deferred income tax liability - non-current			(77,899)
Total identifiable net assets			736,224
Goodwill			0	[7]
Consideration transferred			736,224
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables			181,826	[3]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables, Gross Contractual Amount			183,769	[3]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Uncollectable Receivables			1,943	[3]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory Adjustment			16,900	[3]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Power Purchase Agreement Liability, Weighted Average Life	36 months	[2]
Trademarks and Trade Names [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	20 years
Intangible assets:
Intangible assets			40,170
Developed Technology Rights [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	20 years
Intangible assets:
Intangible assets			31,600
Other Intangible Assets [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	9 years 4 months 24 days
Intangible assets:
Intangible assets			$ 1,422

[1] None of the cash held in escrow is considered contingent consideration as it is expected to be released to the Sellers pending the Sellers’ satisfaction of general representations and warranties made in connection with the execution of the purchase agreement.

[2] Vinnolit’s long-term debt paid on behalf of the Sellers was not legally assumed by Westlake in the acquisition and was a condition of the consummation of the purchase agreement. Therefore, the retirement has been included in the total purchase consideration.

[3] The fair value of accounts receivable acquired is $181,826, with the gross contractual amount being $183,769. The Company expects $1,943 to be uncollectible.

[4] An adjustment of approximately $16,900 was recorded to reflect Vinnolit's inventories at fair value and increased cost of sales by the same amount for the three months ended September 30, 2014.

[5] Included in other assets was a loan acquired that was repaid prior to September 30, 2014.

[6] A liability arising from unfavorable forward purchase contracts for the purchase of power was recognized at fair value. This liability will be amortized over a period of approximately 3.0 years, being the weighted-average life of the forward purchase contracts.

[7] Management estimated that the fair value of the net assets acquired equals consideration paid. Therefore, no goodwill was recorded.