Quarterly Results (Schedule Of Quarterly Results) (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Results (Unaudited) [Abstract]
Revenues	$ 512,551	$ 521,324	$ 511,848	$ 566,935	$ 550,145	$ 563,582	$ 437,331	$ 299,359	$ 2,112,658	$ 1,850,417	$ 1,109,557
Costs and expenses	413,098	428,647	428,219	477,847	457,121	471,371	365,892	243,650	1,747,825	1,538,074	909,513
Gain (loss) on disposition of assets	(15)	(40)	69	(28)	(111)	97	40	(66)	(14)	(40)	(78)
Operating income	99,438	92,637	83,698	89,060	92,913	92,308	71,479	55,643	364,833	312,343	200,044
Other income (expense)	(45)	(56)	30	149	183	(6)	78	51	(198)	(41)	273
Interest expense	(6,588)	(6,056)	(5,901)	(5,840)	(5,817)	(5,974)	(3,278)	(2,833)	(24,385)	(17,902)	(10,960)
Earnings before taxes on income	92,805	86,525	77,827	83,369	87,279	86,328	68,279	52,861	340,526	294,747	189,640
Provision for taxes on income	(34,231)	(32,794)	(29,392)	(31,490)	(30,510)	(32,734)	(26,050)	(19,961)	(127,907)	(109,255)	(72,258)
Net earnings	58,574	53,731	48,435	51,879	56,769	53,594	42,229	32,900	212,619	185,492	117,382
Less: Net earnings attributable to noncontrolling interests	(686)	(676)	(884)	(935)	(599)	(860)	(537)	(470)	(3,181)	(2,466)	(1,133)
Net earnings attributable to Kirby	$ 57,888	$ 53,055	$ 47,551	$ 50,944	$ 56,170	$ 52,734	$ 41,692	$ 32,430	$ 209,438	$ 183,026	$ 116,249
Net earnings per share attributable to Kirby common stockholders [Abstract]
Basic (in dollars per share)	$ 1.03	$ 0.95	$ 0.85	$ 0.91	$ 1.01	$ 0.95	$ 0.78	$ 0.60	$ 3.75	$ 3.35	$ 2.16
Diluted (in dollars per share)	$ 1.03	$ 0.95	$ 0.85	$ 0.91	$ 1.00	$ 0.94	$ 0.77	$ 0.60	$ 3.73	$ 3.33	$ 2.15