CONDENSED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net earnings	$ 69,915	$ 40,621
Other comprehensive income (loss), net of taxes:
Pension and postretirement benefits	(395)	(61)
Foreign currency translation adjustments	0	225
Total other comprehensive income (loss), net of taxes	(395)	164
Total comprehensive income, net of taxes	69,520	40,785
Net loss attributable to noncontrolling interests	153	77
Comprehensive income attributable to Kirby	$ 69,673	$ 40,862