CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Statement of Comprehensive Income [Abstract]
Net earnings	$ 286,896	$ 222,905	$ 122,761
Other comprehensive income, net of taxes:
Pension and postretirement benefits	37,043	16,728	43,868
Foreign currency translation adjustments	(857)	1,425	(1,049)
Total other comprehensive income, net of taxes	36,186	18,153	42,819
Total comprehensive income, net of taxes	323,082	241,058	165,580
Net (earnings) loss attributable to noncontrolling interests	(189)	30	(470)
Comprehensive income attributable to Kirby	$ 322,893	$ 241,088	$ 165,110