CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Assets, Current [Abstract]
Cash and cash equivalents	$ 25,104	$ 34,813
Accounts receivable:
Trade - less allowance for doubtful accounts	445,425	417,958
Other	127,181	149,964
Inventories - net	370,385	331,350
Prepaid expense and other current assets	84,160	69,780
Total current assets	1,052,255	1,003,865
Property and equipment	5,416,559	5,392,851
Accumulated depreciation	(1,763,907)	(1,714,336)
Property and equipment - net	3,652,652	3,678,515
Operating lease right-of-use assets	159,968	167,730
Goodwill	438,748	438,748
Other intangibles, net	55,770	60,070
Other assets	45,763	50,135
Total assets	5,405,156	5,399,063
Current liabilities:
Bank notes payable	4,206	1,934
Accounts payable	234,640	199,088
Accrued liabilities	198,191	236,078
Current portion of operating lease liabilities	34,667	33,902
Deferred revenues	69,668	72,770
Total current liabilities	541,372	543,772
Long-term debt, net - less current portion	1,131,849	1,161,433
Deferred income taxes	590,876	574,152
Operating lease liabilities - less current portion	150,355	159,672
Other long-term liabilities	60,960	71,252
Total long-term liabilities	1,934,040	1,966,509
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	854,781	854,512
Accumulated other comprehensive income - net	(21,957)	(25,966)
Retained earnings	2,392,330	2,346,439
Treasury stock - at cost, 5.5 million shares at June 30, 2022 and 5.4 million at December 31, 2021	(304,314)	(295,208)
Total Kirby stockholders' equity	2,927,387	2,886,324
Noncontrolling interests	2,357	2,458
Total equity	2,929,744	2,888,782
Total liabilities and equity	$ 5,405,156	$ 5,399,063