CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net earnings	$ 143,019	$ 79,078	$ 313,903
Other comprehensive income (loss), net of taxes:
Pension and postretirement benefits	(4,203)	7,638	18,748
Foreign currency translation adjustments	(85)	(819)	(146)
Reclassification to retained earnings of stranded tax effects from tax reform	0	(7,925)	0
Total other comprehensive income (loss), net of taxes	(4,288)	(1,106)	18,602
Total comprehensive income, net of taxes	138,731	77,972	332,505
Net earnings attributable to noncontrolling interests	(672)	(626)	(716)
Comprehensive income attributable to Kirby	$ 138,059	$ 77,346	$ 331,789