Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]
Net earnings attributable to Kirby	$ 64,267	$ 69,123	$ 63,093	$ 56,578	$ 57,888	$ 53,055	$ 47,551	$ 50,944	$ 253,061	$ 209,438	$ 183,026
Undistributed earnings allocated to restricted shares									(1,819)	(1,618)	(1,613)
Income available to Kirby common stockholders - basic									251,242	207,820	181,413
Undistributed earnings allocated to restricted shares									1,819	1,618	1,613
Undistributed earnings reallocated to restricted shares									(1,813)	(1,612)	(1,606)
Income available to Kirby common stockholders - diluted									$ 251,248	$ 207,826	$ 181,420
Weighted average common stock issued and outstanding (in shares)									56,762	55,897	54,673
Weighted average unvested restricted stock (in shares)									(408)	(431)	(482)
Weighted average common stock outstanding - basic (in shares)									56,354	55,466	54,191
Dilutive effect of stock options (in shares)									198	208	222
Weighted average common stock outstanding - diluted (in shares)									56,552	55,674	54,413
Net earnings per share attributable to Kirby common stockholders [Abstract]
Basic (in dollars per share)	$ 1.13	$ 1.22	$ 1.11	$ 1.00	$ 1.03	$ 0.95	$ 0.85	$ 0.91	$ 4.46	$ 3.75	$ 3.35
Diluted (in dollars per share)	$ 1.13	$ 1.21	$ 1.11	$ 1.00	$ 1.03	$ 0.95	$ 0.85	$ 0.91	$ 4.44	$ 3.73	$ 3.33
Antidilutive Securities Excluded from Computation of Earnings Per Share (in shares)									2,000	100,000	2,000