CONDENSED STATEMENTS OF EARNINGS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues:
Total revenues	$ 496,850	$ 643,926
Costs and expenses:
Costs of sales and operating expenses	363,040	453,568
Selling, general and administrative	69,629	72,080
Taxes, other than on income	8,260	11,406
Depreciation and amortization	54,890	55,786
Impairments and other charges	0	561,274
Gain on disposition of assets	(2,133)	(492)
Total costs and expenses	493,686	1,153,622
Operating income (loss)	3,164	(509,696)
Other income	3,791	2,723
Interest expense	(10,966)	(12,799)
Loss before taxes on income	(4,011)	(519,772)
Benefit for taxes on income	891	172,809
Net loss	(3,120)	(346,963)
Less: Net earnings attributable to noncontrolling interests	(255)	(278)
Net loss attributable to Kirby	$ (3,375)	$ (347,241)
Net loss per share attributable to Kirby common stockholders:
Basic (in dollars per share)	$ (0.06)	$ (5.80)
Diluted (in dollars per share)	$ (0.06)	$ (5.80)
Marine Transportation [Member]
Revenues:
Total revenues	$ 300,951	$ 403,257
Distribution and Services [Member]
Revenues:
Total revenues	$ 195,899	$ 240,669