CONDENSED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
CONDENSED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) [Abstract]
Net earnings		$ 28,789	$ 32,353	$ 82,406	$ 109,946
Other comprehensive income (loss), net of taxes:
Pension and postretirement benefits		507	735	15,393	(1,765)
Foreign currency translation adjustments	[1]	(164)	0	(164)	0
Total other comprehensive income (loss), net of taxes		343	735	15,229	(1,765)
Total comprehensive income, net of taxes		29,132	33,088	97,635	108,181
Net earnings attributable to noncontrolling interests		(182)	(343)	(538)	(895)
Comprehensive income attributable to Kirby		$ 28,950	$ 32,745	$ 97,097	$ 107,286

[1] Actuarial gains/(losses) are amortized into costs of sales and operating expenses or selling, general and administrative expenses as appropriate. (See Note 11 - Retirement Plans)