CONDENSED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
CONDENSED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) [Abstract]
Net earnings (loss)	$ 25,263	$ 47,440	$ (321,700)	$ 91,897
Other comprehensive income (loss), net of taxes:
Pension and postretirement benefits	(2,477)	6,057	(2,395)	6,468
Foreign currency translation adjustments	351	(53)	(923)	76
Total other comprehensive income (loss), net of taxes	(2,126)	6,004	(3,318)	6,544
Total comprehensive income (loss), net of taxes	23,137	53,444	(325,018)	98,441
Net earnings attributable to noncontrolling interests	(261)	(153)	(539)	(314)
Comprehensive income (loss) attributable to Kirby	$ 22,876	$ 53,291	$ (325,557)	$ 98,127