CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Assets, Current [Abstract]
Cash and cash equivalents	$ 26,699	$ 80,577
Accounts receivable:
Trade - less allowance for doubtful accounts	526,489	483,406
Other	109,539	114,556
Inventories - net	475,218	461,848
Prepaid expense and other current assets	62,421	71,372
Total current assets	1,200,366	1,211,759
Property and equipment	5,532,952	5,452,143
Accumulated depreciation	(1,867,442)	(1,818,681)
Property and equipment - net	3,665,510	3,633,462
Operating lease right-of-use assets	155,306	154,507
Goodwill	438,748	438,748
Other intangibles, net	49,325	51,463
Other assets	65,493	64,985
Total assets	5,574,748	5,554,924
Current liabilities:
Bank notes payable	3,983	3,292
Income taxes payable	1,106	323
Accounts payable	278,467	278,081
Accrued liabilities	173,992	204,752
Current portion of operating lease liabilities	32,885	36,444
Deferred revenues	124,355	119,305
Total current liabilities	614,788	642,197
Long-term debt, net - less current portion	1,075,658	1,076,326
Deferred income taxes	638,438	625,884
Operating lease liabilities - less current portion	146,445	142,140
Other long-term liabilities	14,279	23,209
Total long-term liabilities	1,874,820	1,867,559
Contingencies and commitments	0	0
Kirby stockholders' equity:
Common stock, $0.10 par value per share. Authorized 120 million shares, issued 65.5 million shares	6,547	6,547
Additional Paid in Capital	856,680	859,345
Accumulated other comprehensive income - net	17,017	16,853
Retained earnings	2,509,428	2,468,730
Treasury stock - at cost, 5.5 million shares at March 31, 2023 and 5.6 million at December 31, 2022	(306,746)	(308,598)
Total Kirby stockholders' equity	3,082,926	3,042,877
Noncontrolling interests	2,214	2,291
Total equity	3,085,140	3,045,168
Total liabilities and equity	$ 5,574,748	$ 5,554,924