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Agreements with Westlake and Related Parties (Details)
12 Months Ended
Oct. 28, 2025
Aug. 04, 2014
USD ($)
lease
lb
$ / lb
Dec. 31, 2025
USD ($)
lb
$ / lb
Dec. 31, 2024
USD ($)
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]        
Term of Investment Management Agreement with Related Party, Maximum     9 months  
IMA, Partnership earned amount added to market rate, basis points     five  
Receivables under Investment Management Agreements with Related Parties, Current | $     $ 23,378,000 $ 134,557,000
Westlake Chemical OpCo LP | Ethylene Sales Agreement | Investee        
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]        
Long-Term Purchase Commitment, Renewal Term 12 months      
Westlake Chemical OpCo LP | Feedstock Supply Agreement | Investee        
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]        
Long-Term Purchase Commitment, Renewal Term 12 months      
Westlake Chemical OpCo LP | Exchange Agreement        
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]        
Purchase commitment, fixed margin on variable pricing | $ / lb     0.006  
Exchange agreement amount of purchase agreement | lb     200,000,000  
Westlake Chemical OpCo LP | Westlake | Ethylene Sales Agreement | Investee        
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]        
Minimum percentage required to be purchased   95.00%    
Maximum mass required to be purchased | lb   3,800,000,000    
Long-term Purchase Commitment, Excess Production Percentage   95.00%    
Number of years used to calculate average expenses   5 years    
Purchase commitment, fixed margin on variable pricing | $ / lb   0.10    
Long-term Purchase Commitment, Curtail Option Percentage   5.00%    
Long-term Purchase Commitment, Compliance Surcharge Amount | $   $ 500,000    
Westlake Chemical OpCo LP | Westlake | Excess Production Option | Investee        
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]        
Purchase commitment, fixed margin on variable pricing | $ / lb   0.10    
Westlake Chemical OpCo LP | Westlake | Feedstock Supply Agreement | Investee        
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]        
Long-Term Purchase Commitment, Renewal Term     12 months  
Westlake Chemical OpCo LP | Westlake | Services And Secondment Agreement | Investee        
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]        
Period of default in performance that can allow a party to terminate agreement   30 days    
Westlake Chemical OpCo LP | Westlake | Site Lease Agreement | Investee        
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]        
Number of lease agreements | lease   2    
Operating lease, rental amount | $   $ 1    
Term of operating lease   50 years