Equipment Acquisitions And Dispositions (Major Equipment Deliveries) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) equipment	Dec. 31, 2015 USD ($) equipment	Dec. 31, 2014 USD ($) equipment
Payments to Acquire Property, Plant, and Equipment | $	$ 358,413	$ 295,930	$ 360,637
Offshore Support Vessels Fast Support [Member]
Number Of Equipments Acquired	12	3	3
Offshore Support Vessels Supply [Member]
Number Of Equipments Acquired	2	1	2
Offshore Support Vessels Specialty [Member]
Number Of Equipments Acquired	1	0	0
Wind Farm Utility Vessel [Member]
Number Of Equipments Acquired	2	2	2
Offshore Support Vessels [Member]
Number Of Equipments Acquired	17	6	7
Inland River Dry Cargo Barges [Member]
Number Of Equipments Acquired	46	0	65
Inland River Liquid Tank Barges - 10,000 Barrel [Member]
Number Of Equipments Acquired	0	8	0
Inland River Specialty Barges [Member]
Number Of Equipments Acquired	0	4	0
Inland River Towboats [Member]
Number Of Equipments Acquired	2	9	1
U S Flag Tankers [Member]
Number Of Equipments Acquired	3	0	0
Short-sea Container\RORO Vessels [Member]
Number Of Equipments Acquired	0	0	1
U.S.-flag Harbor Tugs [Member]
Number Of Equipments Acquired	1	0	0
Central Contracting & Marine, Inc. [Member]
Number Of Equipments Acquired	5
Cypress CKOR LLC [Member]
Number Of Equipments Acquired	1
Cypress CKOR LLC [Member] | Offshore Support Vessels [Member]
Number Of Equipments Acquired	1
SeaJon II [Member]
Number Of Equipments Acquired	1
Fair Value Hedging [Member]
Payments to Acquire Property, Plant, and Equipment | $	$ 358,786