Quarterly Results (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Results (Unaudited) [Abstract]
Revenues	$ 708,111	$ 541,274	$ 473,328	$ 491,705	$ 435,650	$ 434,708	$ 441,582	$ 458,733	$ 2,214,418	$ 1,770,673	$ 2,147,532
Costs and expenses	755,990	487,753	425,708	446,233	378,684	378,400	374,868	393,399	2,120,171	1,525,478	1,766,870
Gain (loss) on disposition of assets	(4,288)	(159)	(139)	99	(166)	(122)	94	67	(4,487)	(127)	1,672
Operating income	(52,167)	53,362	47,481	45,571	56,800	56,186	66,808	65,401	94,247	245,195	380,662
Other income (expense)	469	(113)	(1)	(116)	47	(120)	179	135	(52)	(291)	(663)
Interest expense	(7,162)	(5,388)	(4,465)	(4,457)	(4,477)	(4,507)	(4,513)	(4,193)	(21,472)	(17,690)	(18,738)
Earnings before taxes on income	(58,860)	47,861	43,015	40,998	52,370	51,559	62,474	61,343	73,014	227,746	361,712
Benefit (provision) for taxes on income	290,357	(19,072)	(17,043)	(13,353)	(19,512)	(19,206)	(23,365)	(22,859)	240,889	(84,942)	(133,742)
Net earnings	231,497	28,789	25,972	27,645	32,858	32,353	39,109	38,484	313,903	142,804	227,970
Less: Net earnings attributable to noncontrolling interests	(178)	(182)	(194)	(162)	(503)	(343)	(167)	(385)	(716)	(1,398)	(1,286)
Net earnings attributable to Kirby	$ 231,319	$ 28,607	$ 25,778	$ 27,483	$ 32,355	$ 32,010	$ 38,942	$ 38,099	$ 313,187	$ 141,406	$ 226,684
Net earnings per share attributable to Kirby common stockholders [Abstract]
Basic (in dollars per share)	$ 3.88	$ 0.52	$ 0.48	$ 0.51	$ 0.60	$ 0.59	$ 0.72	$ 0.71	$ 5.62	$ 2.63	$ 4.12
Diluted (in dollars per share)	$ 3.87	$ 0.52	$ 0.48	$ 0.51	$ 0.60	$ 0.59	$ 0.72	$ 0.71	$ 5.62	$ 2.62	$ 4.11