Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Net Income (Loss) Attributable to Parent [Abstract]
Net earnings (loss) attributable to Kirby	$ 39,091	$ (264,730)	$ 84,982	$ (257,915)
Undistributed earnings allocated to restricted shares	(18)	0	(27)	0
Earnings (loss) available to Kirby common stockholders, basic, total	39,073	(264,730)	84,955	(257,915)
Undistributed earnings allocated to restricted shares	18	0	27	0
Undistributed earnings reallocated to restricted shares	(18)	0	(27)	0
Earnings (loss) available to Kirby common stockholders - diluted	$ 39,073	$ (264,730)	$ 84,955	$ (257,915)
Shares outstanding [Abstract]
Weighted average common stock issued and outstanding (in shares)	59,923	60,109	60,107	60,095
Weighted average unvested restricted stock (in shares)	(27)	(47)	(19)	(51)
Weighted Average Number of Shares Outstanding, Basic (in Shares)	59,896	60,062	60,088	60,044
Dilutive effect of stock options and restricted stock units (in shares)	286	0	281	0
Weighted Average Number of Shares Outstanding, Diluted (in Shares)	60,182	60,062	60,369	60,044
Net earnings per share basic attributable to Kirby common stockholders:
Basic (in dollars per share)	$ 0.65	$ (4.41)	$ 1.41	$ (4.30)
Net earnings per share diluted attributable to Kirby common stockholders:
Diluted (in dollars per share)	$ 0.65	$ (4.41)	$ 1.41	$ (4.30)
Antidilutive securities excluded from computation of earnings per share (in shares)			400,000	600,000
RSUs [Member]
Net earnings per share diluted attributable to Kirby common stockholders:
Antidilutive securities excluded from computation of earnings per share (in shares)			11,000	565,000