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Earnings Per Share (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Earnings Per Share [Abstract]                      
Net earnings attributable to Kirby $ 32,355 $ 32,010 $ 38,942 $ 38,099 $ 50,688 $ 56,843 $ 58,075 $ 61,078 $ 141,406 $ 226,684 $ 282,006
Undistributed earnings allocated to restricted shares                 (999) (1,345) (1,643)
Income available to Kirby common stockholders - basic                 140,407 225,339 280,363
Undistributed earnings allocated to restricted shares                 999 1,345 1,643
Undistributed earnings reallocated to restricted shares                 (997) (1,343) (1,637)
Income available to Kirby common stockholders - diluted                 $ 140,409 $ 225,341 $ 280,369
Shares Outstanding [Abstract]                      
Weighted average common stock issued and outstanding (in shares)                 53,834 55,056 57,006
Weighted average unvested restricted stock (in shares)                 (380) (327) (332)
Weighted average common stock outstanding - basic (in shares)                 53,454 54,729 56,674
Dilutive effect of stock options (in shares)                 58 97 193
Weighted average common stock outstanding - diluted (in shares)                 53,512 54,826 56,867
Net earnings per share attributable to Kirby common stockholders [Abstract]                      
Basic (in dollars per share) $ 0.60 $ 0.59 $ 0.72 $ 0.71 $ 0.94 $ 1.04 $ 1.04 $ 1.09 $ 2.63 $ 4.12 $ 4.95
Diluted (in dollars per share) $ 0.60 $ 0.59 $ 0.72 $ 0.71 $ 0.94 $ 1.04 $ 1.04 $ 1.09 $ 2.62 $ 4.11 $ 4.93
Antidilutive securities excluded from computation of earnings per share (in shares)                 240,000 227,000 75,000