v3.26.1
Debt Obligations - Schedule of Notes Payable (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2026
Dec. 31, 2025
Jun. 30, 2025
Long Term Debt [Line Items]      
Variable rate (as a percent) 3.68% 3.87%  
Gross amount of debt $ 2,281,784 $ 2,732,168  
Less: unamortized debt issuance costs and note discounts (28,079) (31,830)  
Total debt obligations 2,253,705 2,700,338  
Line of Credit | Revolving credit facility      
Long Term Debt [Line Items]      
Debt instrument, face amount $ 1,750,000    
Credit facility at a floating rate of interest of one-month term Secured Overnight Financing Rate (“SOFR”) plus 2.35% at March 31, 2026, secured by engines, airframes, and loan assets. The credit facility has a committed amount of $1.75 billion at March 31, 2026, which revolves until the maturity date of April 2031.      
Long Term Debt [Line Items]      
Variable rate (as a percent) 2.35%    
Line of credit facility outstanding amount $ 421,000 $ 650,000  
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 333,561 $ 337,400  
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 54,869 $ 55,500  
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 509,988 514,720  
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 $ 70,075 70,725  
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 $ 127,149 225,797  
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 $ 223,366 225,896  
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 $ 31,009 31,360  
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 $ 6,889 7,446  
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 $ 207,175 210,351  
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 $ 28,861 29,303  
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 $ 4,918 5,538  
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 $ 83,483 142,640  
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 $ 11,295 19,152  
Willis Warehouse Facility LLC (“WWFL”) credit facility was terminated during the three months ended March 31, 2026      
Long Term Debt [Line Items]      
Gross amount of debt 0 82,655  
Other Fixed Rate Engine Notes Due March 2032 and April 2034      
Long Term Debt [Line Items]      
Gross amount of debt $ 168,146 $ 123,685  
Other Fixed Rate Engine Notes Due March 2032 and April 2034 | Minimum      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 4.23%    
Other Fixed Rate Engine Notes Due March 2032 and April 2034 | Maximum      
Long Term Debt [Line Items]      
Fixed rate (as a percent) 5.91%