EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
EARNINGS PER SHARE [Abstract]
Net earnings attributable to Kirby	$ 62,246	$ 56,578
Undistributed earnings allocated to restricted shares	(370)	(401)
Income available to Kirby common stockholders - basic	61,876	56,177
Undistributed earnings allocated to restricted shares	370	401
Undistributed earnings reallocated to restricted shares	(368)	(399)
Income available to Kirby common stockholders - diluted	$ 61,878	$ 56,179
Weighted average common stock issued and outstanding (in shares)	56,903,000	56,669,000
Weighted average unvested restricted stock (in shares)	(338,000)	(401,000)
Weighted average common stock outstanding - basic (in shares)	56,565,000	56,268,000
Dilutive effect of stock options (in shares)	216,000	187,000
Weighted average common stock outstanding - diluted (in shares)	56,781,000	56,455,000
Net earnings per share attributable to Kirby common stockholders:
Basic (in dollars per share)	$ 1.09	$ 1.00
Diluted (in dollars per share)	$ 1.09	$ 1.00
Antidilutive Securities Excluded from Computation of Earnings Per Share (in shares)	75,000	209,000