v3.26.1
Earnings Per Share (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Net Income (Loss) Attributable to Parent [Abstract]        
Net earnings attributable to Kirby $ 89,729 $ 94,277 $ 170,926 $ 170,263
Undistributed earnings allocated to restricted shares (13) (17) (12) (15)
Earnings available to Kirby common stockholders - basic 89,716 94,260 170,914 170,248
Undistributed earnings allocated to restricted shares 13 17 12 15
Undistributed earnings reallocated to restricted shares (13) (17) (12) (15)
Earnings available to Kirby common stockholders - diluted $ 89,716 $ 94,260 $ 170,914 $ 170,248
Shares outstanding [Abstract]        
Weighted average common stock issued and outstanding (in shares) 53,382,000 56,115,000 53,521,000 56,525,000
Weighted average unvested restricted stock (in shares) (7,000) (10,000) (3,000) (5,000)
Weighted average common stock outstanding - basic (in shares) 53,375,000 56,105,000 53,518,000 56,520,000
Dilutive effect of stock options and restricted stock units (in shares) 321,000 332,000 336,000 349,000
Weighted average common stock outstanding - diluted 53,696,000 56,437,000 53,854,000 56,869,000
Net earnings per share basic attributable to Kirby common stockholders:        
Basic $ 1.68 $ 1.68 $ 3.19 $ 3.01
Net earnings per share diluted attributable to Kirby common stockholders:        
Diluted $ 1.67 $ 1.67 $ 3.17 $ 2.99
RSUs [Member]        
Net earnings per share diluted attributable to Kirby common stockholders:        
Antidilutive securities excluded from computation of earnings per share (in shares) 0 0 0 0
Stock Options [Member]        
Net earnings per share diluted attributable to Kirby common stockholders:        
Antidilutive securities excluded from computation of earnings per share (in shares) 0 0 0 0