CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets, Current [Abstract]
Cash and cash equivalents	$ 32,398	$ 34,813
Accounts receivable:
Trade - less allowance for doubtful accounts	420,823	417,958
Other	125,757	149,964
Inventories - net	360,457	331,350
Prepaid expense and other current assets	75,896	69,780
Total current assets	1,015,331	1,003,865
Property and equipment	5,391,988	5,392,851
Accumulated depreciation	(1,731,674)	(1,714,336)
Property and equipment - net	3,660,314	3,678,515
Operating lease right-of-use assets	164,986	167,730
Goodwill	438,748	438,748
Other intangibles, net	57,934	60,070
Other assets	45,479	50,135
Total assets	5,382,792	5,399,063
Current liabilities:
Bank notes payable	3,097	1,934
Income taxes payable	93	0
Accounts payable	218,907	199,088
Accrued liabilities	188,302	236,078
Current portion of operating lease liabilities	34,454	33,902
Deferred revenues	68,982	72,770
Total current liabilities	513,835	543,772
Long-term debt, net - less current portion	1,151,638	1,161,433
Deferred income taxes	580,014	574,152
Operating lease liabilities - less current portion	156,271	159,672
Other long-term liabilities	69,169	71,252
Total long-term liabilities	1,957,092	1,966,509
Contingencies and commitments
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	853,610	854,512
Accumulated other comprehensive income - net	(25,477)	(25,966)
Retained earnings	2,363,873	2,346,439
Treasury stock - at cost, 5.2 million shares at March 31, 2022 and 5.4 million at December 31, 2021	(289,098)	(295,208)
Total Kirby stockholders' equity	2,909,455	2,886,324
Noncontrolling interests	2,410	2,458
Total equity	2,911,865	2,888,782
Total liabilities and equity	$ 5,382,792	$ 5,399,063