Acquisitions (Details) (USD $)	12 Months Ended				0 Months Ended	12 Months Ended		0 Months Ended				0 Months Ended						0 Months Ended	12 Months Ended		0 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 28, 2012 Flag Service & Maintenance, Inc [Member]	Dec. 14, 2012 Penn Maritime Inc. and Maritime Investments LLC [Member] MMBbls	Dec. 31, 2012 Penn Maritime Inc. and Maritime Investments LLC [Member]	Dec. 14, 2012 Penn Maritime Inc. and Maritime Investments LLC [Member] Tugboats [Member]	Jul. 02, 2011 K-Sea Transportation Partners L.P. [Member] MMBbls	Jun. 28, 2011 K-Sea Transportation Partners L.P. [Member]	Jun. 28, 2011 K-Sea Transportation Partners L.P. [Member] Tank Barges [Member]	Jun. 28, 2011 K-Sea Transportation Partners L.P. [Member] Tugboats [Member]	Apr. 15, 2011 United Holdings LLC [Member]	Dec. 15, 2011 Seaboats, Inc. [Member]	Dec. 15, 2011 Seaboats, Inc. [Member] Tank Barges [Member] bbl	Feb. 24, 2011 Enterprise Marine Services LLC [Member]	Feb. 24, 2011 Enterprise Marine Services LLC [Member] Tank Barges [Member]	Feb. 24, 2011 Enterprise Marine Services LLC [Member] Towboat [Member]	Nov. 01, 2012 Allied Transportation Company [Member] bbl	Dec. 31, 2012 Allied Transportation Company [Member]	Nov. 01, 2012 Allied Transportation Company [Member] Tank Barges [Member]	Nov. 01, 2012 Allied Transportation Company [Member] Offshore Dry Bulk Barges [Member] T	Nov. 01, 2012 Allied Transportation Company [Member] Coastal Tugboats [Member]	Feb. 09, 2011 Kinder Morgan Petcoke, L.P. [Member]
Business acquisition, consideration transferred [Abstract]
Cash consideration paid				$ 5,100,000	$ 145,855,000				$ 227,617,000			$ 271,192,000	$ 42,745,000		$ 53,200,000			$ 107,014,000					$ 4,050,000
Total value of transaction					300,192,000				603,427,000
Stock consideration through issuance of Company common stock					29,080,000				113,019,000
Issue of common stock (in shares)					500,000			1,939,234
Shares issued per share (in dollars per share)					$ 58.16				$ 58.28
Number of doubled hulled tank barges					18			54
Capacity, in barrels, of purchased productive assets (in barrels)					1.9			3.8						80,000				680,000
Number of productive assets purchased							16			57	63			3		21	15			10	3	7
Useful life of purchased productive assets					13 years			9 years
Goodwill						84,203,000													22,817,000
Net intangibles						22,600,000													8,600,000
Weighted average amortization period						14 years 10 months 24 days							5 years						18 years 10 months 24 days
Expected goodwill will be deductible for tax purposes (in hundredths)						30.00%
Cash to retire outstanding debt					125,257,000				262,791,000
Selling, General and Administrative Expense	178,483,000	170,386,000	117,694,000			728,000													244,000
Capacity, in deadweight tons of purchased productive assets																					48,000
Acquisition and integration related costs																		10,000,000
Fair value of contingent earnout provision payable in 2014																		9,756,000
Earnout provisional for payment to additional payables												50,000,000
Number of operational locations												21
Number of operational states												7
Percentage of ownership acquired (in hundredths)																							51.00%
Noncontrolling interest attributable to parent (in hundredths)																							49.00%
Purchase price of towboat																							1,250,000
Entity's pro forma revenues [Abstract]
Revenues	2,112,658,000	2,105,904,000	1,685,173,000
Net earnings attributable to Kirby	$ 209,438,000	$ 172,426,000	$ 123,981,000
Net earnings per share attributable to Kirby common stockholders [Abstract]
Basic (in dollars per share)	$ 3.75	$ 3.10	$ 2.22
Diluted (in dollars per share)	$ 3.73	$ 3.09	$ 2.22