v3.26.1
Fair Value of Investments - Schedule of Changes in Fair Value of Financial Instruments for Level 3 Inputs to Determine Fair Value (Details) - USD ($)
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Transfers into Level 3 $ 0 $ 0 $ 0 $ 0
Transfers out of Level 3 0 0 0 0
Private Debt        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 899,048,000 637,395,000 884,414,000 490,462,000
Purchases of investments (including PIK, if any) 81,174,000 88,143,000 117,417,000 244,826,000
Proceeds from principal repayments and sales of investments (57,073,000) (49,913,000) (77,700,000) (61,873,000)
Accretion of discount/amortization of premium 600,000 535,000 1,533,000 891,000
Total gains or losses included in earnings   996,000   2,850,000
Ending balance 921,452,000 677,156,000 921,452,000 677,156,000
Net change in unrealized appreciation (depreciation) on non-controlled/ non-affiliated company investments $ (2,316,000) $ 996,000 $ (4,085,000) $ 2,850,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]   Non-controlled, non-affiliated investments   Non-controlled, non-affiliated investments
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Non-controlled, non-affiliated investments Non-controlled, non-affiliated investments Non-controlled, non-affiliated investments Non-controlled, non-affiliated investments
Private Debt | Location, Statement of Income, Balance [Axis]: wt:RealizedGainLossInvestmentAndForeignCurrencyTransactionOperatingBeforeTax        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gains or losses included in earnings $ 74,000   $ 74,000  
Private Debt | Location, Statement of Income, Balance [Axis]: wt:UnrealizedGainLossInvestmentAndDerivativeOperatingAndForeignCurrencyTransactionBeforeTax        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gains or losses included in earnings $ (2,371,000)   $ (4,286,000)  
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Non-controlled, non-affiliated investments   Non-controlled, non-affiliated investments