Investments, At Equity, And Advances To 50% Or Less Owned Companies (Summary of Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jun. 01, 2018	Apr. 30, 2018	Dec. 31, 2017	Sep. 01, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 156,886			$ 173,441
Trailer Bridge
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest						55.30%
RF Vessel Holdings
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest					50.00%
Golfo de Mexico
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest					50.00%
KSM
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	50.00%
Hawker Pacific
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest			34.20%
Ocean Services
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 73,940			52,003
Ocean Services | Trailer Bridge
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	55.30%
Equity method investments	$ 56,364			47,324
Ocean Services | RF Vessel Holdings
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	50.00%
Equity method investments	$ 10,826			2,378
Ocean Services | Golfo de Mexico
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	50.00%
Equity method investments	$ 5,272			2,500
Ocean Services | KSM
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	50.00%
Equity method investments	$ 1,478			(199)
Inland Services
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 57,897			66,479
Inland Services | SCFCo
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	50.00%
Equity method investments	$ 37,219			42,126
Inland Services | Bunge-SCF Grain
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	50.00%
Equity method investments	$ 14,738			16,166
Inland Services | SCF Bunge Marine
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	57.00%
Equity method investments	$ 3,144			5,404
Inland Services | Other
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	50.00%
Equity method investments	$ 2,796			2,783
Witt O'Brien's LLC | O’Brien’s do Brazil
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	50.00%
Equity method investments	$ 472			777
Other
Schedule of Equity Method Investments [Line Items]
Equity method investments	24,577			54,182
Other | Other
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 1,214			2,371
Other | Other | Minimum
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	34.00%
Other | Other | Maximum
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	47.50%
Other | Hawker Pacific
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest			34.20%
Equity method investments	$ 0			21,681
Other | VA&E
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	41.30%
Equity method investments	$ 13,073			13,596
Other | Avion
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest	39.10%
Equity method investments	$ 10,290			11,400
Other | Cleancor
Schedule of Equity Method Investments [Line Items]
Ownership of equity interest		50.00%
Equity method investments	$ 0			$ 5,134