CONDENSED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CONDENSED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net loss	$ (3,120)	$ (346,963)
Other comprehensive income (loss), net of taxes:
Pension and postretirement benefits	745	82
Foreign currency translation adjustments	(497)	(1,274)
Total other comprehensive income (loss), net of taxes	248	(1,192)
Total comprehensive loss, net of taxes	(2,872)	(348,155)
Net earnings attributable to noncontrolling interests	(255)	(278)
Comprehensive loss attributable to Kirby	$ (3,127)	$ (348,433)