v3.26.1
Investments - Additional Information (Details)
 1 Months Ended 3 Months Ended 6 Months Ended
Dec. 31, 2025
USD ($)
Mar. 31, 2025
USD ($)
Jun. 30, 2026
USD ($)
engine
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
engine
aircraft
lease
Jun. 30, 2025
USD ($)
Jun. 30, 2025
engine
Jun. 30, 2025
airframe
Schedule of Equity Method Investments [Line Items]                
Currency translation adjustment balance $ 1,400,000   $ 700,000   $ 700,000      
Management and advisory fees     5,524,000 $ 2,588,000 13,419,000 $ 4,551,000    
Technical expense     9,947,000 7,508,000 19,635,000 13,738,000    
Payment for fleet management services         1,400,000      
Management and advisory fee income     2,800,000   7,700,000      
Due from affiliates 0   3,188,000   3,188,000      
Due to affiliates 0   1,407,000   1,407,000      
Equity method investments 0   10,578,000   10,578,000      
Unfunded capital commitments     35,300,000   35,300,000      
Capital commitments is expected funded by certain executives and employees     10,000,000.0   10,000,000.0      
Related Party                
Schedule of Equity Method Investments [Line Items]                
Due to affiliates     1,400,000   1,400,000      
Equipment Held For Operating Lease                
Schedule of Equity Method Investments [Line Items]                
Fund value 2,801,683,000   $ 2,783,382,000   $ 2,783,382,000      
CASC Willis Engine Lease Company Limited                
Schedule of Equity Method Investments [Line Items]                
Ownership interest     50.00%   50.00%      
Number of engines in lease portfolio | engine         6      
Number of assets sold | engine         0   1  
Proceeds from sale of assets           6,100,000    
Gain on sale of asset           0    
CASC Willis Engine Lease Company Limited | Equipment Held For Operating Lease                
Schedule of Equity Method Investments [Line Items]                
Fund value     $ 51,500,000   $ 51,500,000      
Willis Mitsui And Company Engine Support Limited                
Schedule of Equity Method Investments [Line Items]                
Number of engines in lease portfolio | engine         75      
Number of aircrafts in lease portfolio | aircraft         2      
Management and advisory fees     $ 2,000,000.0 1,800,000 $ 3,900,000 3,000,000.0    
Number of assets purchased | engine         0      
Purchases from related party           7,200,000    
Lessee, operating lease, number of engines subleased | engine     2   2      
Number of leases renewed | lease         1      
Technical expense     $ 700,000 700,000 $ 1,400,000 1,300,000    
Contributions         $ 29,500,000      
Willis Mitsui And Company Engine Support Limited | Transaction One                
Schedule of Equity Method Investments [Line Items]                
Number of assets sold         5   3 1
Proceeds from sale of assets         $ 55,300,000 32,200,000    
Gain on sale of asset         15,300,000 1,600,000    
Willis Mitsui And Company Engine Support Limited | Transaction Two                
Schedule of Equity Method Investments [Line Items]                
Number of assets sold | engine             1  
Proceeds from sale of assets           21,100,000    
Gain on sale of asset           1,400,000    
Willis Mitsui And Company Engine Support Limited | Equipment Held For Operating Lease                
Schedule of Equity Method Investments [Line Items]                
Fund value     713,800,000   713,800,000      
Willis Global Engine Testing                
Schedule of Equity Method Investments [Line Items]                
Ownership interest   70.00%            
Maximum loss exposure   $ 4,100,000            
Committed amount   $ 22,400,000            
China Aviation Supplies Import & Export Corporation Willis Lease Company Limited                
Schedule of Equity Method Investments [Line Items]                
Management and advisory fees     $ 200,000 $ 0 $ 200,000 $ 0    
Liberty Mutual Investments                
Schedule of Equity Method Investments [Line Items]                
Committed amount $ 600,000,000              
Ownership interest percentage 10.00%              
Blackstone Credit And Insurance                
Schedule of Equity Method Investments [Line Items]                
Committed amount $ 1,000,000,000              
Number of assets sold | engine         14      
Proceeds from sale of assets         $ 216,200,000      
Gain on sale of asset         $ 33,300,000      
Ownership interest percentage 17.50%              
Willis Aviation Lending Warehouse I LLC                
Schedule of Equity Method Investments [Line Items]                
Number of assets sold | engine         12      
Proceeds from sale of assets         $ 104,000,000.0      
Gain on sale of asset         $ 600,000