v3.26.1
Earnings Per Share - Approach to Calculate Diluted Earnings Per Share (Detail) - USD ($)
$ / shares in Units, shares in Thousands, $ in Millions
 3 Months Ended 9 Months Ended
May 31, 2026
May 31, 2025
May 31, 2026
May 31, 2025
Earnings Per Share [Abstract]        
Net Income (Loss) $ 18.9 $ 60.1 $ 70.3 $ 167.3
Weighted average basic common shares outstanding 30,938 31,186 30,936 31,269
Basic earnings per share $ 0.61 $ 1.92 $ 2.27 $ 5.35
Net earnings attributable to Greenbrier $ 18.9 $ 60.1 $ 70.3 $ 167.3
Weighted average diluted common shares outstanding 31,745 32,184 31,781 32,272
Diluted earnings per share $ 0.6 $ 1.86 $ 2.21 $ 5.18