ACCOUNTING STANDARDS ADOPTIONS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements [Abstract]
Operating expense	$ 636,888	$ 488,345	$ 2,074,674	$ 1,360,082
Nonoperating expense	(1,454)	(320)	(4,586)	41
Statements of earnings [Abstract]
Revenues	704,845	541,274	2,249,204	1,506,307
Costs of sales and operating expenses	498,421	378,750	1,640,366	1,048,299
Operating income	67,957	52,929	174,530	146,225
Earnings before taxes on income	57,066	47,861	144,451	131,874
Provision for taxes on income	(15,116)	(19,072)	(41,042)	(49,468)
Net earnings attributable to Kirby	41,816	28,607	102,889	81,868
Statements of comprehensive income [Abstract]
Net earnings	41,950	28,789	103,409	82,406
Comprehensive income attributable to Kirby	42,194	28,950	95,750	97,097
Statements of cash flows [Abstract]
Net earnings	41,950	28,789	103,409	82,406
Provision for deferred income taxes			36,838	32,783
Decrease in cash flows resulting from changes in operating assets and liabilities, net			(66,707)	(28,592)
Balance sheets [Abstract]
Trade receivables	400,870		400,870		$ 452,222
Inventories - net	453,173		453,173		315,729
Total assets	5,854,332		5,854,332		5,127,427
Deferred revenues	75,843		75,843		48,347
Deferred income taxes	544,882		544,882		468,451
Retained earnings	2,748,029		2,748,029		2,646,937
Total liabilities and equity	5,854,332		5,854,332		$ 5,127,427
Distribution and Services [Member]
Statements of earnings [Abstract]
Revenues	322,805	222,464	1,148,598	512,580
ASU 2018-02 [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
New Accounting Pronouncements [Abstract]
Reclassification from AOCI to retained earnings	(7,925)		(7,925)
ASU 2018-02 [Member] | Retained Earnings [Member]
New Accounting Pronouncements [Abstract]
Reclassification from AOCI to retained earnings	7,925		7,925
ASU 2017-07 [Member]
New Accounting Pronouncements [Abstract]
Operating expense		(433)		(189)
Nonoperating expense		$ 433		$ 189
ASC 606 [Member] | Balances without Adoption of ASC 606 [Member]
Statements of earnings [Abstract]
Costs of sales and operating expenses	520,721		1,645,166
Operating income	72,657		175,530
Earnings before taxes on income	61,766		145,451
Provision for taxes on income	(16,282)		(41,295)
Net earnings attributable to Kirby	45,350		103,636
Statements of comprehensive income [Abstract]
Net earnings	45,484		104,156
Comprehensive income attributable to Kirby	45,728		96,497
Statements of cash flows [Abstract]
Net earnings	45,484		104,156
Provision for deferred income taxes			36,585
Decrease in cash flows resulting from changes in operating assets and liabilities, net			(67,201)
Balance sheets [Abstract]
Trade receivables	466,599		466,599
Inventories - net	395,773		395,773
Total assets	5,862,661		5,862,661
Deferred revenues	70,372		70,372
Deferred income taxes	548,235		548,235
Retained earnings	2,758,476		2,758,476
Total liabilities and equity	5,862,661		5,862,661
ASC 606 [Member] | Balances without Adoption of ASC 606 [Member] | Distribution and Services [Member]
Statements of earnings [Abstract]
Revenues	349,805		1,154,398
ASC 606 [Member] | Effect of Change [Member]
Statements of earnings [Abstract]
Costs of sales and operating expenses	(22,300)		(4,800)
Operating income	(4,700)		(1,000)
Earnings before taxes on income	(4,700)		(1,000)
Provision for taxes on income	1,166		253
Net earnings attributable to Kirby	(3,534)		(747)
Statements of comprehensive income [Abstract]
Net earnings	(3,534)		(747)
Comprehensive income attributable to Kirby	(3,534)		(747)
Statements of cash flows [Abstract]
Net earnings	(3,534)		(747)
Provision for deferred income taxes			253
Decrease in cash flows resulting from changes in operating assets and liabilities, net			494
Balance sheets [Abstract]
Trade receivables	(65,729)		(65,729)
Inventories - net	57,400		57,400
Total assets	(8,329)		(8,329)
Deferred revenues	5,471		5,471
Deferred income taxes	(3,353)		(3,353)
Retained earnings	(10,447)		(10,447)
Total liabilities and equity	(8,329)		(8,329)
ASC 606 [Member] | Effect of Change [Member] | Distribution and Services [Member]
Statements of earnings [Abstract]
Revenues	(27,000)		(5,800)
ASC 606 [Member] | Retained Earnings [Member]
New Accounting Pronouncements [Abstract]
Cumulative effect on retained earnings	$ (9,722)		$ (9,722)