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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Data Type:	xbrli:stringItemType
Balance Type:	na
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- Definition

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

+ References

No definition available.

+ Details

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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=118260190&loc=d3e13433-108611

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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=6877327&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

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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

- Definition

Amount of cash outflow for payment of an obligation from a lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

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-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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

- 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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Long-Term Debt (Credit Agreement) (Details) - USD ($) $ in Millions				6 Months Ended
	Jun. 04, 2020	Mar. 20, 2020	Jul. 24, 2018	Jun. 30, 2020	Jun. 30, 2019
Debt Instrument [Line Items]
Repayments of Lines of Credit				$ 1,000	$ 0
Credit Agreement [Member] \| Line of Credit [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Line of credit permitted increase			$ 25
Credit Agreement [Member] \| Line of Credit [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Line of credit permitted increase			500
Credit Agreement [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Remaining borrowing capacity				1,000
Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity				1,000
Proceeds from Lines of Credit		$ 1,000
Repayments of Lines of Credit	$ 1,000
Line of Credit Facility, Fair Value of Amount Outstanding				0
Outstanding letters of credit				$ 0
Credit Agreement [Member] \| Letter of Credit [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity			150
Credit Agreement [Member] \| Swingline Loan [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 50
Credit Agreement [Member] \| Alternate Base Rate [Domain] \| Revolving Credit Facility [Member] \| Line of Credit [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Spread on variable rate			0.00%
Credit Agreement [Member] \| Alternate Base Rate [Domain] \| Revolving Credit Facility [Member] \| Line of Credit [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Spread on variable rate			0.75%
Credit Agreement [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member] \| Line of Credit [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Spread on variable rate			1.00%
Credit Agreement [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member] \| Line of Credit [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Spread on variable rate			1.75%