Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- 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

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value of the amount outstanding under the credit facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The permitted amount the line of credit facility may be increased by, under certain circumstances if certain lenders agree to commit to such an increase.

+ References

No definition available.

+ Details

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Namespace Prefix:	wlk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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- Details

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- Details

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- Details

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Long-Term Debt (Credit Agreement) (Details) - Credit Agreement [Member] - USD ($) $ in Millions	Jul. 24, 2018	Jun. 30, 2021
Line of Credit \| Minimum
Debt Instrument [Line Items]
Line of credit permitted increase	$ 25
Line of Credit \| Maximum
Debt Instrument [Line Items]
Line of credit permitted increase	500
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Remaining borrowing capacity		$ 1,000
Revolving Credit Facility [Member] \| Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity		1,000
Line of Credit Facility, Fair Value of Amount Outstanding		0
Outstanding letters of credit		$ 0
Letter of Credit [Member] \| Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	150
Swingline Loan [Member] \| Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 50
Alternate Base Rate [Domain] \| Revolving Credit Facility [Member] \| Line of Credit \| Minimum
Debt Instrument [Line Items]
Spread on variable rate	0.00%
Alternate Base Rate [Domain] \| Revolving Credit Facility [Member] \| Line of Credit \| Maximum
Debt Instrument [Line Items]
Spread on variable rate	0.75%
London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member] \| Line of Credit \| Minimum
Debt Instrument [Line Items]
Spread on variable rate	1.00%
London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member] \| Line of Credit \| Maximum
Debt Instrument [Line Items]
Spread on variable rate	1.75%