v3.26.1
N-2 - $ / shares
3 Months Ended
Mar. 31, 2026
Dec. 31, 2025
Mar. 31, 2025
Dec. 31, 2024
Cover [Abstract]        
Entity Central Index Key 0002020354      
Amendment Flag false      
Securities Act File Number 814-01758      
Document Type 10-Q      
Entity Registrant Name West Bay BDC LLC      
Entity Address, Address Line One 200 West Street      
Entity Address, City or Town New York      
Entity Address, State or Province NY      
Entity Address, Postal Zip Code 10282      
City Area Code 312      
Local Phone Number 655-4419      
Entity Emerging Growth Company true      
Entity Ex Transition Period true      
General Description of Registrant [Abstract]        
Investment Objectives and Practices [Text Block]

The Company’s investment objective is to generate current income and, to a lesser extent, long-term capital appreciation primarily through direct originations of secured debt, including first lien, unitranche, and last-out portions of such loans, second lien debt, unsecured debt, including mezzanine debt, and select equity investments.

     
Risk Factors [Table Text Block]

ITEM 1A. RISK FACTORS.

An investment in our securities involves a high degree of risk. There have been no material changes to the risk factors previously reported under Item 1A. “Risk Factors” of our annual report on Form 10-K for the year ended December 31, 2025, which was filed with the SEC on March 3, 2026. Additional risks and uncertainties not currently known to us or that we currently deem to be immaterial may materially affect our business, financial condition and/or operating results.

     
NAV Per Share [1] $ 17.51 $ 17.33 $ 17.29 $ 17.36
SCB Revolving Credit Facility        
Capital Stock, Long-Term Debt, and Other Securities [Abstract]        
Long Term Debt, Title [Text Block]

We entered into a revolving credit facility on September 25, 2024 with Standard Chartered Bank Ltd., as administrative agent (the “Administrative Agent”), lead arranger, sole bookrunner, letter of credit issuer and lender (as amended, supplemented or otherwise modified and in effect from time to time, the “SCB Revolving Credit Facility”). We entered into the first amendment (the “Amendment”) to the SCB Revolving Credit Facility on January 30, 2026. The Amendment, among other things, (i) increased the maximum commitment amount to $400,000, (ii) extended the stated maturity date from September 25, 2026 to September 24, 2027 and (iii) decreased the applicable margin (a) with respect to Term SOFR Loans, alternative currency term rate loans, daily CORRA loans, daily SONIA loans and letters of credit, to 1.85% per annum, and (b) with respect to base rate loans, to 0.85% per annum.

Subject to availability under the Borrowing Base (as defined in the SCB Revolving Credit Facility), the maximum principal amount of the SCB Revolving Credit Facility is $400 million. The Borrowing Base is calculated based on the unfunded capital commitments of the Unitholders (subject to various eligibility requirements) multiplied by the specified advance rate of 75%. The stated maturity date of the SCB Revolving Credit Facility is September 24, 2027.

Under the SCB Revolving Credit Facility, we have the ability to elect, for loans denominated in U.S. dollars, either Term SOFR with a one- or three- months tenor or the alternative base rate at the time of draw-down (and with respect to loans denominated in non-U.S. dollar currencies, the applicable benchmark specified in the SCB Revolving Credit Facility), and loans denominated in U.S. dollars may be converted from one rate to another at any time, subject to certain conditions. The interest rate on obligations under the SCB Revolving Credit Facility is (A) Term SOFR for the applicable tenor (or other listed offered rate, depending upon the currency of borrowing) plus 1.85% per annum or (B) an alternative base rate (the greatest of the prime rate set by the Administrative Agent, the federal funds rate plus 0.50%, and Term SOFR with a one-month tenor plus 1.00%) plus 0.85% per annum, with a floor of 0%.

For further details on our SCB Revolving Credit Facility, see Note 6 “Debt—SCB Revolving Credit Facility” to our financial statements included in this report.

     
Long Term Debt, Structuring [Text Block] The stated maturity date of the SCB Revolving Credit Facility is September 24, 2027.

Under the SCB Revolving Credit Facility, we have the ability to elect, for loans denominated in U.S. dollars, either Term SOFR with a one- or three- months tenor or the alternative base rate at the time of draw-down (and with respect to loans denominated in non-U.S. dollar currencies, the applicable benchmark specified in the SCB Revolving Credit Facility), and loans denominated in U.S. dollars may be converted from one rate to another at any time, subject to certain conditions. The interest rate on obligations under the SCB Revolving Credit Facility is (A) Term SOFR for the applicable tenor (or other listed offered rate, depending upon the currency of borrowing) plus 1.85% per annum or (B) an alternative base rate (the greatest of the prime rate set by the Administrative Agent, the federal funds rate plus 0.50%, and Term SOFR with a one-month tenor plus 1.00%) plus 0.85% per annum, with a floor of 0%.

     
[1] The per Unit data was derived by using the weighted average Units outstanding during the applicable period, except for distributions recorded, which reflects the actual amount of distribution recorded per Unit for the applicable period.