Quarterly Results (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Results (Unaudited) [Abstract]
Revenues	$ 721,493	$ 704,845	$ 802,671	$ 741,688	$ 708,111	$ 541,274	$ 473,328	$ 491,705
Costs and expenses	740,344	636,906	747,260	692,866	756,423	488,186	425,937	445,760
Gain (loss) on disposition of assets	(390)	18	442	1,898	(4,288)	(159)	(139)	99	$ 1,968	$ (4,487)	$ (127)
Operating income	(19,241)	67,957	55,853	50,720	(52,600)	52,929	47,252	46,044	155,289	93,625	247,370
Nonoperating expense	1,140	1,454	1,541	1,591	902	320	228	(589)
Interest expense	(12,191)	(12,345)	(12,540)	(9,780)	(7,162)	(5,388)	(4,465)	(4,457)	(46,856)	(21,472)	(17,690)
Earnings before taxes on income	(30,292)	57,066	44,854	42,531	(58,860)	47,861	43,015	40,998	114,159	73,014	227,746
Benefit (provision) for taxes on income	5,961	(15,116)	(16,061)	(9,865)	290,357	(19,072)	(17,043)	(13,353)	(35,081)	240,889	(84,942)
Net earnings	(24,331)	41,950	28,793	32,666	231,497	28,789	25,972	27,645	79,078	313,903	142,804
Less: Net earnings attributable to noncontrolling interests	(106)	(134)	(191)	(195)	(178)	(182)	(194)	(162)	(626)	(716)	(1,398)
Net earnings attributable to Kirby	$ (24,437)	$ 41,816	$ 28,602	$ 32,471	$ 231,319	$ 28,607	$ 25,778	$ 27,483	$ 78,452	$ 313,187	$ 141,406
Net earnings per share attributable to Kirby common stockholders [Abstract]
Basic (in dollars per share)	$ (0.41)	$ 0.70	$ 0.48	$ 0.54	$ 3.88	$ 0.52	$ 0.48	$ 0.51	$ 1.31	$ 5.62	$ 2.63
Diluted (in dollars per share)	$ (0.41)	$ 0.70	$ 0.48	$ 0.54	$ 3.87	$ 0.52	$ 0.48	$ 0.51	$ 1.31	$ 5.62	$ 2.62