Equipment Acquisitions And Dispositions (Major Equipment Dispositions) (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) equipment	Dec. 31, 2015 USD ($) equipment	Dec. 31, 2014 USD ($) equipment
Offshore Support Vessels Standby Safety [Member]
Number of Equipments Removed from Service	4	0	0
Offshore Support Vessels Anchor Handling Towing Supply [Member]
Number of Equipments Removed from Service	0	0	1
Offshore Support Vessels Fast Support [Member]
Number of Equipments Removed from Service	0	1	7
Offshore Support Vessels Supply [Member]
Number of Equipments Removed from Service	5	1	4
Liftboats [Member]
Number of Equipments Removed from Service	0	0	1
Wind Farm Utility Vessel [Member]
Number of Equipments Removed from Service	0	0	1
Offshore Support Vessels [Member]
Number of Equipments Removed from Service	9	2	14
Inland River Dry Cargo Barges [Member]
Number of Equipments Removed from Service	0	0	80
Inland River Liquid Tank Barges - 10,000 Barrel [Member]
Number of Equipments Removed from Service	0	35	0
Inland River Liquid Tank Barges - 30,000 Barrel [Member]
Number of Equipments Removed from Service	19	0	0
Inland River Deck Barges [Member]
Number of Equipments Removed from Service | $	0	12	0
Inland River Towboats [Member]
Number of Equipments Removed from Service	14	4	5
U.S.-flag Product Tankers [Member]
Number of Equipments Removed from Service	1	0	1
Short-sea Container\RORO Vessels [Member]
Number of Equipments Removed from Service	0	0	2
U.S.-flag Harbor Tugs [Member]
Number of Equipments Removed from Service	2	0	0