v3.26.1
Debt Obligations - Schedule of Notes Payable (Details) - USD ($)
 6 Months Ended 12 Months Ended
Jun. 30, 2026
Dec. 31, 2025
May 31, 2026
Long Term Debt [Line Items]      
Variable rate (as a percent) 3.68% 3.87%  
Gross amount of debt $ 2,352,269,000 $ 2,732,168,000  
Less: unamortized debt issuance costs and note discounts (31,365,000) (31,830,000)  
Total debt obligations 2,320,904,000 2,700,338,000  
Line of Credit | Revolving credit facility      
Long Term Debt [Line Items]      
Debt instrument, face amount $ 1,750,000,000    
Credit facility at a floating rate of interest of one-month term Secured Overnight Financing Rate (“SOFR”) plus 1.875% at June 30, 2026, secured by engines, airframes, and loan assets. The credit facility has a committed amount of $1.75 billion at June 30, 2026, which revolves until the maturity date of April 2031.      
Long Term Debt [Line Items]      
Variable rate (as a percent) 1.875%    
Line of credit facility outstanding amount $ 437,000,000 650,000,000  
WEST IX Series A 2025 term notes payable at a fixed rate of interest of 5.16%, maturing in December 2050, secured by engines, airframes, and loan assets      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 5.16%    
Gross amount of debt $ 329,323,000 337,400,000  
WEST IX Series B 2025 term note payable at a fixed rate of interest of 5.70%, maturing in December 2050, secured by engines, airframes, and loan assets      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 5.70%    
Gross amount of debt $ 54,171,000 55,500,000  
WEST VIII Series A 2025 term notes payable at a fixed rate of interest of 5.58%, maturing in June 2050, secured by engines, airframes, and loan assets      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 5.58%    
Gross amount of debt $ 505,581,000 514,720,000  
WEST VIII Series B 2025 term note payable at a fixed rate of interest of 6.07%, maturing in June 2050, secured by engines, airframes, and loan assets      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 6.07%    
Gross amount of debt $ 69,469,000 70,725,000  
WEST VII Series A 2023 term notes payable at a fixed rate of interest of 8.00%, maturing in October 2048, secured by engines, airframes, and loan assets      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 8.00%    
Gross amount of debt $ 26,000,000 225,797,000  
WEST VI Series A 2021 term notes payable at a fixed rate of interest of 3.10%, maturing in May 2046, secured by engines, airframes, and loan assets      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 3.10%    
Gross amount of debt $ 220,849,000 225,896,000  
WEST VI Series B 2021 term notes payable at a fixed rate of interest of 5.44%, maturing in May 2046, secured by engines, airframes, and loan assets      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 5.44%    
Gross amount of debt $ 30,659,000 31,360,000  
WEST VI Series C 2021 term notes payable at a fixed rate of interest of 7.39%, maturing in May 2046, secured by engines, airframes, and loan assets      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 7.39%    
Gross amount of debt $ 6,336,000 7,446,000  
WEST V Series A 2020 term notes payable at a fixed rate of interest of 3.23%, maturing in March 2045, secured by engines      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 3.23%    
Gross amount of debt $ 203,999,000 210,351,000  
WEST V Series B 2020 term notes payable at a fixed rate of interest of 4.21%, maturing in March 2045, secured by engines      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 4.21%    
Gross amount of debt $ 28,418,000 29,303,000  
WEST V Series C 2020 term notes payable at a fixed rate of interest of 6.66%, maturing in March 2045, secured by engines      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 6.66%    
Gross amount of debt $ 4,300,000 5,538,000  
WEST III Series A 2017 term notes payable at a fixed rate of interest of 4.69%, maturing in August 2042, secured by engines      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 4.69%    
Gross amount of debt $ 60,921,000 142,640,000  
WEST III Series B 2017 term notes payable at a fixed rate of interest of 6.36%, maturing in August 2042, secured by engines      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 6.36%    
Gross amount of debt $ 8,239,000 19,152,000  
Willis Warehouse Facility LLC (“WWFL”) credit facility was terminated during the six months ended June 30, 2026      
Long Term Debt [Line Items]      
Gross amount of debt $ 0 82,655,000  
Convertible senior notes at a fixed rate of interest of 2.50%, maturing in May 2031      
Long Term Debt [Line Items]      
Debt instrument, face amount     $ 200,000,000.0
Fixed rate (as a percent) 2.50%   2.50%
Gross amount of debt $ 200,000,000 0  
Other fixed-rate engine notes (interest between 4.23% and 5.91%, and maturity dates between March 2032 and April 2034)      
Long Term Debt [Line Items]      
Gross amount of debt $ 167,004,000 $ 123,685,000  
Other fixed-rate engine notes (interest between 4.23% and 5.91%, and maturity dates between March 2032 and April 2034) | Minimum      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 4.23%    
Other fixed-rate engine notes (interest between 4.23% and 5.91%, and maturity dates between March 2032 and April 2034) | Maximum      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 5.91%