CONDENSED STATEMENTS OF EARNINGS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Total revenues	$ 704,845	$ 541,274	$ 2,249,204	$ 1,506,307
Costs and expenses:
Costs of sales and operating expenses	498,421	378,750	1,640,366	1,048,299
Selling, general and administrative	70,032	51,712	239,416	144,404
Taxes, other than on income	10,523	6,518	29,610	19,511
Depreciation and amortization	57,930	51,206	167,640	147,669
Loss (gain) on disposition of assets	(18)	159	(2,358)	199
Total costs and expenses	636,888	488,345	2,074,674	1,360,082
Operating income	67,957	52,929	174,530	146,225
Other income (expense)	1,454	320	4,586	(41)
Interest expense	(12,345)	(5,388)	(34,665)	(14,310)
Earnings before taxes on income	57,066	47,861	144,451	131,874
Provision for taxes on income	(15,116)	(19,072)	(41,042)	(49,468)
Net earnings	41,950	28,789	103,409	82,406
Less: Net earnings attributable to noncontrolling interests	(134)	(182)	(520)	(538)
Net earnings attributable to Kirby	$ 41,816	$ 28,607	$ 102,889	$ 81,868
Net earnings per share attributable to Kirby common stockholders:
Basic (in dollars per share)	$ 0.70	$ 0.52	$ 1.72	$ 1.51
Diluted (in dollars per share)	$ 0.70	$ 0.52	$ 1.72	$ 1.50
Marine Transportation [Member]
Revenues:
Total revenues	$ 382,040	$ 318,810	$ 1,100,606	$ 993,727
Distribution and Services [Member]
Revenues:
Total revenues	$ 322,805	$ 222,464	$ 1,148,598	$ 512,580