CONDENSED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net earnings	$ 90,031	$ 63,004	$ 243,928	$ 160,943
Other comprehensive income (loss), net of taxes:
Pension and postretirement benefits	(484)	(61)	107	1,152
Foreign currency translation adjustments	(22)	143	(495)	1,073
Total other comprehensive income (loss), net of taxes	(506)	82	(388)	2,225
Total comprehensive income, net of taxes	89,525	63,086	243,540	163,168
Net (earnings) loss attributable to noncontrolling interests	(63)	(40)	(38)	86
Comprehensive income attributable to Kirby	$ 89,462	$ 63,046	$ 243,502	$ 163,254