v3.26.3
Debt, Net - Additional Information (Detail) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
1 Months Ended 12 Months Ended
Jan. 31, 2026
Nov. 30, 2023
Feb. 28, 2022
Aug. 31, 2026
Feb. 28, 2026
Aug. 31, 2025
Aug. 31, 2024
Feb. 01, 2024
Debt Instrument [Line Items]                
Debt instrument amount outstanding       $ 1,855.3        
European                
Debt Instrument [Line Items]                
Line of credit, guaranteed amount       $ 59.0        
European | Maximum                
Debt Instrument [Line Items]                
Line of credit maturity date       2028-09        
European | Minimum                
Debt Instrument [Line Items]                
Line of credit maturity date       2026-10        
Mexico                
Debt Instrument [Line Items]                
Line of credit facility maximum capacity       $ 56.0        
Mexico | Maximum                
Debt Instrument [Line Items]                
Line of credit maturity date       2029-07        
Mexico | Minimum                
Debt Instrument [Line Items]                
Line of credit maturity date       2027-01        
WIBOR | European | Maximum                
Debt Instrument [Line Items]                
Debt instrument, percentage points added to the reference rate       1.25%        
WIBOR | European | Minimum                
Debt Instrument [Line Items]                
Debt instrument, percentage points added to the reference rate       1.20%        
EURIBOR | European | Maximum                
Debt Instrument [Line Items]                
Debt instrument, percentage points added to the reference rate       1.90%        
EURIBOR | European | Minimum                
Debt Instrument [Line Items]                
Debt instrument, percentage points added to the reference rate       1.00%        
2.875% Convertible senior notes, due 2028                
Debt Instrument [Line Items]                
Debt instrument, effective interest rate       5.75%        
Debt instrument, interest rate       2.875%   2.875% 2.875%  
Description of long term debt       The 2028 Convertible Notes bear interest at a fixed rate of 2.875%, paid semiannually in arrears on April 15th and October 15th.        
Debt instrument, maturity date       Apr. 15, 2028        
Convertible notes initial conversion rate, shares per $1,000 principal amount       0.18214        
Debt instrument, convertible, principal amount       $ 1,000.0        
Convertible notes conversion rate, per share       $ 54.9        
Number of shares reserved for future issuance       8.1        
2.875% Convertible senior notes, due 2028 | Redemption on or After April 15, 2025                
Debt Instrument [Line Items]                
Debt instrument, convertible, latest date       Jan. 15, 2028        
Debt instrument redemption start date       Apr. 15, 2025        
Debt instrument redemption end date       Apr. 15, 2028        
Debt instrument, convertible, threshold percentage of stock price trigger       130.00%        
Debt instrument redemption description       Additionally, the Company may elect to call the notes on or after April 15, 2025 and on or before the 40th trading day prior to April 15, 2028, at a cash redemption price described in the 2028 Notes Indenture if the stock price exceeds 130% of the conversion price during certain trading days as defined in the 2028 Notes Indenture.        
2.875% Convertible senior notes, due 2024                
Debt Instrument [Line Items]                
Debt instrument, interest rate       2.875%   2.875% 2.875% 2.875%
Corporate Senior Term Debt                
Debt Instrument [Line Items]                
Debt instrument, maturity month and year       2030-05        
Periodic Principal Payment       $ 3.1        
Balloon payment       $ 190.6        
Swap agreement interest rate       70.00%        
Corporate Senior Term Debt | SOFR                
Debt Instrument [Line Items]                
Debt instrument, percentage points added to the reference rate       1.50%        
Leasing Senior Term Debt                
Debt Instrument [Line Items]                
Periodic Principal Payment       $ 2.6        
Balloon payment       $ 237.0        
Swap agreement interest rate       100.00%        
Leasing Senior Term Debt | SOFR                
Debt Instrument [Line Items]                
Debt instrument, percentage points added to the reference rate       1.625%        
European Debt                
Debt Instrument [Line Items]                
Line of credit facility maximum capacity $ 50.3              
Line of credit maturity date 2031-01              
European Debt | EURIBOR                
Debt Instrument [Line Items]                
Debt instrument, percentage points added to the reference rate 3.50%              
GBX Leasing Warehouse Facility | GBXL I Series 2022-1 Notes                
Debt Instrument [Line Items]                
Debt, Principal amount     $ 323.3          
Debt instrument, maturity month and year     2022-02          
Debt instruments additional interest rate per annum       4.00%        
GBX Leasing Warehouse Facility | GBXL I Series 2022-1 Notes | GBXL I Series 2022-1 Class A Secured Railcar Equipment Notes                
Debt Instrument [Line Items]                
Debt instrument, interest rate       2.87%        
GBX Leasing Warehouse Facility | GBXL I Series 2022-1 Notes | GBXL I Series 2022-1 Class B Secured Railcar Equipment Notes                
Debt Instrument [Line Items]                
Debt instrument, interest rate       3.45%        
GBX Leasing Warehouse Facility | 2022 GBXL Notes                
Debt Instrument [Line Items]                
Frequency of payments       monthly        
Debt instrument, maturity date       Feb. 20, 2052        
Debt instrument, repayment date       Jan. 20, 2029        
Debt instrument, maturity year       2052        
GBX Leasing Warehouse Facility | 2023 GBXL Notes                
Debt Instrument [Line Items]                
Debt, Principal amount   $ 178.5            
Debt instrument, maturity month and year   2023-11            
Frequency of payments       monthly        
Debt instrument, maturity date       Nov. 20, 2053        
Debt instrument, repayment date       Nov. 20, 2030        
Debt instruments additional interest rate per annum       4.00%        
GBX Leasing Warehouse Facility | 2023 GBXL Notes | GBXL I Series 2023-1 Class A Secured Railcar Equipment Notes                
Debt Instrument [Line Items]                
Debt instrument, interest rate       6.42%        
Debt instrument, maturity year       2053        
GBX Leasing Warehouse Facility | 2023 GBXL Notes | GBXL I Series 2023-1 Class B Secured Railcar Equipment Notes                
Debt Instrument [Line Items]                
Debt instrument, interest rate       7.28%        
GBX Leasing Warehouse Facility | 2026 GBXL Notes                
Debt Instrument [Line Items]                
Debt, Principal amount         $ 300.0      
Frequency of payments       monthly        
Debt instrument, maturity date       Feb. 22, 2056        
Debt instrument, repayment date       Feb. 21, 2033        
Debt instrument, maturity year       2056        
GBX Leasing Warehouse Facility | 2026 GBXL Notes | GBXL I Series 2026-1 Class A Secured Railcar Equipment Notes [Member]                
Debt Instrument [Line Items]                
Debt instrument, interest rate       5.13%        
GBX Leasing Warehouse Facility | 2026 GBXL Notes | GBXL I Series 2026-1 Class B Secured Railcar Equipment Notes [Member]                
Debt Instrument [Line Items]                
Debt instrument, interest rate       5.30%        
Revolving Credit Facility | North American                
Debt Instrument [Line Items]                
Line of credit facility maximum capacity       $ 600.0        
Aggregate amount available to draw down       428.5        
Letters of Credit Outstanding, Amount       $ 51.1   $ 5.4    
Revolving Credit Facility | North American | Maximum                
Debt Instrument [Line Items]                
Line of credit maturity date       2030-05        
Revolving Credit Facility | European                
Debt Instrument [Line Items]                
Line of credit facility maximum capacity       $ 130.5        
Aggregate amount available to draw down       37.7        
Revolving Credit Facility | Mexico                
Debt Instrument [Line Items]                
Line of credit facility maximum capacity       156.0        
Aggregate amount available to draw down       $ 136.0        
Joint venture partner each guaranteed percentage       50.00%        
Revolving Credit Facility | Prime Rate | North American                
Debt Instrument [Line Items]                
Debt instrument, percentage points added to the reference rate       0.50%        
Revolving Credit Facility | SOFR | North American                
Debt Instrument [Line Items]                
Debt instrument, percentage points added to the reference rate       1.50%        
Mexican Railcar Manufacturing Operations Line of Credit 2, 3rd Component of Senior Secured Credit Facilities | Mexico                
Debt Instrument [Line Items]                
Debt instrument, percentage points added to the reference rate       2.00%        
Mexican Railcar Manufacturing Operations Line of Credit 1, 3rd Component of Senior Secured Credit Facilities | Mexico                
Debt Instrument [Line Items]                
Debt instrument, percentage points added to the reference rate       3.80%        
Leasing Warehouse Credit Facility                
Debt Instrument [Line Items]                
Line of credit maturity date       2029-09        
Leasing Warehouse Credit Facility | North American                
Debt Instrument [Line Items]                
Line of credit facility maximum capacity       $ 450.0        
Leasing Warehouse Credit Facility | SOFR                
Debt Instrument [Line Items]                
Debt instrument, percentage points added to the reference rate       1.70%        
Delayed Draw Facility | Leasing Senior Term Debt                
Debt Instrument [Line Items]                
Line of credit facility maximum capacity       $ 125.0