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Supplemental Information (Cash Flow Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Capital expenditures incurred but not yet paid	$ 3,243	$ 9,863	$ 7,809
Interest paid	23,237	26,528	24,537
Income taxes paid	873	831	827
Right-of-use assets obtained in exchange for operating lease obligations	920	758	5,079
Reimbursement to Parent for State Tax | Westlake | Affiliated Entity
Related Party Transaction [Line Items]
Income taxes paid	333	351	347
State and Local Jurisdiction
Related Party Transaction [Line Items]
Income taxes paid	$ 540	$ 480	$ 480

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