ACCOUNTING STANDARDS ADOPTIONS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements [Abstract]
Operating expense	$ 746,818	$ 426,076	$ 1,437,786	$ 871,737
Nonoperating expense	(1,541)	(228)	(3,132)	361
Statements of earnings [Abstract]
Revenues	802,671	473,328	1,544,359	965,033
Costs of sales and operating expenses	588,628	324,750	1,141,945	669,549
Operating income	55,853	47,252	106,573	93,296
Earnings before taxes on income	44,854	43,015	87,385	84,013
Provision for taxes on income	(16,061)	(17,043)	(25,926)	(30,396)
Net earnings attributable to Kirby	28,602	25,778	61,073	53,261
Statements of comprehensive income [Abstract]
Net earnings	28,793	25,972	61,459	53,617
Comprehensive income attributable to Kirby	28,160	39,918	53,556	68,147
Statements of cash flows [Abstract]
Net earnings	28,793	25,972	61,459	53,617
Provision for deferred income taxes			23,381	18,651
Decrease in cash flows resulting from changes in operating assets and liabilities, net			(63,484)	8,585
Balance sheets [Abstract]
Trade receivables	448,281		448,281		$ 452,222
Inventories - net	384,007		384,007		315,729
Total assets	5,829,276		5,829,276		5,127,427
Deferred revenues	61,165		61,165		48,347
Deferred income taxes	531,284		531,284		468,451
Retained earnings	2,706,213		2,706,213		2,646,937
Total liabilities and equity	5,829,276		5,829,276		$ 5,127,427
Distribution and Services [Member]
Statements of earnings [Abstract]
Revenues	424,508	142,063	825,793	290,116
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		(229)		(244)
Nonoperating expense		$ 229		$ 244
ASC 606 [Member] | Balances without Adoption of ASC 606 [Member]
Statements of earnings [Abstract]
Costs of sales and operating expenses	549,628		1,124,445
Operating income	46,353		102,873
Earnings before taxes on income	35,354		83,685
Provision for taxes on income	(13,797)		(25,013)
Net earnings attributable to Kirby	21,366		58,286
Statements of comprehensive income [Abstract]
Net earnings	21,557		58,672
Comprehensive income attributable to Kirby	20,924		50,769
Statements of cash flows [Abstract]
Net earnings	21,557		58,672
Provision for deferred income taxes			24,294
Decrease in cash flows resulting from changes in operating assets and liabilities, net			(61,610)
Balance sheets [Abstract]
Trade receivables	487,499		487,499
Inventories - net	248,907		248,907
Total assets	5,833,394		5,833,394
Deferred revenues	56,183		56,183
Deferred income taxes	533,471		533,471
Retained earnings	2,713,126		2,713,126
Total liabilities and equity	5,833,394		5,833,394
ASC 606 [Member] | Balances without Adoption of ASC 606 [Member] | Distribution and Services [Member]
Statements of earnings [Abstract]
Revenues	376,008		804,593
ASC 606 [Member] | Effect of Change [Member]
Statements of earnings [Abstract]
Costs of sales and operating expenses	39,000		17,500
Operating income	9,500		3,700
Earnings before taxes on income	9,500		3,700
Provision for taxes on income	(2,264)		(913)
Net earnings attributable to Kirby	7,236		2,787
Statements of comprehensive income [Abstract]
Net earnings	7,236		2,787
Comprehensive income attributable to Kirby	7,236		2,787
Statements of cash flows [Abstract]
Net earnings	7,236		2,787
Provision for deferred income taxes			(913)
Decrease in cash flows resulting from changes in operating assets and liabilities, net			(1,874)
Balance sheets [Abstract]
Trade receivables	(39,218)		(39,218)
Inventories - net	35,100		35,100
Total assets	(4,118)		(4,118)
Deferred revenues	4,982		4,982
Deferred income taxes	(2,187)		(2,187)
Retained earnings	(6,193)		(6,193)
Total liabilities and equity	(4,118)		(4,118)
ASC 606 [Member] | Effect of Change [Member] | Distribution and Services [Member]
Statements of earnings [Abstract]
Revenues	48,500		21,200
ASC 606 [Member] | Retained Earnings [Member]
New Accounting Pronouncements [Abstract]
Cumulative effect on retained earnings	$ (9,722)		$ (9,722)