CONDENSED STATEMENTS OF EARNINGS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues:
Total revenues	$ 598,920	$ 496,567	$ 1,655,394	$ 1,681,652
Costs and expenses:
Costs of sales and operating expenses	446,519	340,764	1,219,038	1,167,871
Selling, general and administrative	66,065	61,720	198,434	199,412
Taxes, other than on income	9,917	9,077	28,541	33,548
Depreciation and amortization	53,462	54,779	163,484	165,067
Impairments and other charges	340,713	0	340,713	561,274
(Gain) loss on disposition of assets	(830)	316	(5,082)	(13)
Total costs and expenses	915,846	466,656	1,945,128	2,127,185
Operating income (loss)	(316,926)	29,911	(289,734)	(445,533)
Other income	1,832	1,172	8,146	6,185
Interest expense	(10,500)	(11,809)	(32,172)	(37,316)
Earnings (loss) before taxes on income	(325,594)	19,274	(313,760)	(476,664)
Benefit for taxes on income	60,442	8,419	55,840	182,657
Net earnings (loss)	(265,152)	27,693	(257,920)	(294,007)
Net (earnings) loss attributable to noncontrolling interests	422	(204)	5	(743)
Net earnings (loss) attributable to Kirby	$ (264,730)	$ 27,489	$ (257,915)	$ (294,750)
Net earning (loss) per share attributable to Kirby common stockholders:
Basic (in dollars per share)	$ (4.41)	$ 0.46	$ (4.30)	$ (4.92)
Diluted (in dollars per share)	$ (4.41)	$ 0.46	$ (4.30)	$ (4.92)
Marine Transportation [Member]
Revenues:
Total revenues	$ 338,514	$ 320,602	$ 972,352	$ 1,104,846
Distribution and Services [Member]
Revenues:
Total revenues	$ 260,406	$ 175,965	$ 683,042	$ 576,806