Investments, At Equity, And Advances To 50% Or Less Owned Companies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) equipment	Dec. 31, 2015 USD ($) equipment shares	Dec. 31, 2014 USD ($) equipment	Dec. 02, 2016	Nov. 30, 2016 USD ($)	Jun. 01, 2015
Schedule of Equity Method Investments [Line Items]
Cumulative undistributed net earnings of 50% or less owned companies accounted for by the equity method included in the Company's consolidated retained earnings	$ 7,800,000	$ 19,900,000
Proceeds from Issuance of Secured Debt	8,000,000	1,700,000	$ 45,300,000
Equity Method Investment, Other than Temporary Impairment	14,700,000		3,300,000
Letters of Credit Outstanding, Amount	26,200,000
Guarantor Obligations, Maximum Exposure, Undiscounted	1,900,000
Asset Impairment Charges	130,800,000	7,100,000	4,400,000
MexMar [Member]
Schedule of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions	$ 7,400,000	7,900,000	$ 2,900,000
Number Of Equipments Acquired	2		2
Repayments of Secured Debt		15,000,000	$ 10,700,000
Property, Plant and Equipment, Additions	$ 34,000,000		32,000,000
Payments to Acquire Machinery and Equipment			6,400,000
Proceeds from Issuance of Secured Debt			25,600,000
Related Party Transaction, Revenues from Transactions with Related Party	300,000	400,000	300,000
Related party transaction expense	5,100,000	11,600,000	13,500,000
Falcon Global [Member]
Schedule of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions	7,700,000	15,700,000	3,400,000
Equity Method Investment, Other than Temporary Impairment	$ 6,400,000
Equity Method Investment, Ownership Percentage	50.00%
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 51,800,000
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	6,400,000
Sea-Cat Crewzer II [Member]
Schedule of Equity Method Investments [Line Items]
Related Party Transaction, Revenues from Transactions with Related Party	700,000	700,000	700,000
Guarantor Obligations, Maximum Exposure, Undiscounted	11,600,000
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital		1,800,000
Partners' Capital Account, Return of Capital			14,000,000
OSV Partners [Member]
Schedule of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions	1,200,000	1,400,000	5,100,000
Related Party Transaction, Revenues from Transactions with Related Party	$ 500,000	1,200,000	1,200,000
Equity Method Investment, Ownership Percentage	30.40%
Sea Cat Crewzer [Member]
Schedule of Equity Method Investments [Line Items]
Related Party Transaction, Revenues from Transactions with Related Party	$ 700,000	700,000	700,000
Related party transaction expense	4,300,000	5,900,000	6,700,000
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 10,300,000
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital		1,300,000	3,300,000
Partners' Capital Account, Return of Capital			3,200,000
Other Offshore Marine Services Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Number of Equipment Operated | equipment	10
Partners' Capital Account, Contributions	$ 500,000		800,000
Repayments of Advances		(200,000)	(600,000)
Related Party Transaction, Revenues from Transactions with Related Party	800,000	800,000	600,000
Equity Method Investment, Other than Temporary Impairment	500,000
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	800,000	900,000	1,000,000
Partners' Capital Account, Return of Capital			200,000
Allocable share of uncalled capital	1,800,000
Guarantee of outstanding charter receivables	400,000
SCFCo Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions	800,000	18,000,000	19,700,000
Proceeds from Issuance of Secured Debt			13,000,000
Repayments of Advances		(14,000,000)	(1,000,000)
Related Party Transaction, Revenues from Transactions with Related Party	100,000	200,000
Equity Method Investment, Other than Temporary Impairment	7,700,000	21,500,000
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	28,500,000
Payments for Advance to Affiliate	1,800,000		23,500,000
Asset Impairment Charges		21,500,000
Advanced to joint ventures	30,300,000
Bunge-SCF Grain [Member]
Schedule of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions			2,000,000
Repayments of Advances		(2,000,000)
Related Party Transaction, Revenues from Transactions with Related Party	1,000,000	1,000,000	1,000,000
Related party transaction expense	7,200,000	10,800,000	7,800,000
Payments for Advance to Affiliate			2,000,000
Advanced to joint ventures	$ 7,000,000
SCF Bunge Marine [Member]
Schedule of Equity Method Investments [Line Items]
Number of Equipment Operated | equipment	6
Related Party Transaction, Revenues from Transactions with Related Party	$ 35,000,000	41,700,000	41,600,000
Related party transaction expense	40,200,000	47,900,000	46,600,000
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	2,500,000	$ 4,000,000	4,500,000
Other Inland River Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Partners' Capital Account, Return of Capital			$ 2,100,000
Dorian LPG [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage		15.90%	16.10%
Business Combination, Separately Recognized Transactions, Net Gains and Losses		$ 32,300,000	$ 4,400,000
Sale of Stock, Number of Shares Issued in Transaction | shares		150,000
Proceeds from Sale and Maturity of Marketable Securities		$ 2,300,000
Trailer Bridge Inc [Member]
Schedule of Equity Method Investments [Line Items]
Repayments of Advances		(18,700,000)	(2,100,000)
Related Party Transaction, Revenues from Transactions with Related Party	$ 300,000	800,000
Equity Method Investment, Ownership Percentage	55.30%
Payments for Advance to Affiliate	$ 1,700,000
Advanced to joint ventures	3,900,000
Business Combination, Separately Recognized Transactions, Net Gains and Losses	(2,200,000)
Sea-Access [Member]
Schedule of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions			16,700,000
Related Party Transaction, Revenues from Transactions with Related Party	500,000	1,000,000	100,000
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	2,000,000	4,400,000
Partners' Capital Account, Return of Capital	8,400,000	8,300,000
SeaJon [Member]
Schedule of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions			2,300,000
Guarantor Obligations, Maximum Exposure, Undiscounted	5,000,000
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	600,000	600,000
Partners' Capital Account, Return of Capital			5,400,000
SeaJon II [Member]
Schedule of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions		1,000,000	600,000
Related Party Transaction, Revenues from Transactions with Related Party	100,000	100,000
Partners' Capital Account, Return of Capital		300,000
Partners' Capital Account, Contributions, Noncash			5,400,000
Business Combination, Separately Recognized Transactions, Net Gains and Losses	1,900,000
Hawker Pacific Airservices Limited [Member]
Schedule of Equity Method Investments [Line Items]
Related Party Transaction, Revenues from Transactions with Related Party	300,000	300,000	500,000
Letters of Credit Outstanding, Amount	6,500,000
VA&E [Member]
Schedule of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions		3,500,000
Repayments of Advances	$ (1,100,000)
Equity Method Investment, Ownership Percentage	41.30%					81.10%
Payments for Advance to Affiliate		1,000,000
Advanced to joint ventures	$ 3,600,000
Line of Credit Facility, Maximum Borrowing Capacity					$ 6,000,000
Proceeds from Unsecured Lines of Credit	10,000,000	15,000,000
Repayments of Long-term Lines of Credit	12,400,000	11,500,000
Avion Pacific Limited [Member]
Schedule of Equity Method Investments [Line Items]
Repayments of Advances		(3,000,000)	(4,000,000)
Payments for Advance to Affiliate	3,000,000		3,000,000
Advanced to joint ventures	3,000,000
Cleancor [Member]
Schedule of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions			4,800,000
Payments for Advance to Affiliate		2,000,000
Advanced to joint ventures	1,900,000
Witt O'Brien's LLC [Member]
Schedule of Equity Method Investments [Line Items]
Related Party Transaction, Revenues from Transactions with Related Party			100,000
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital			400,000
Partners' Capital Account, Return of Capital			400,000
Other Corporate Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions		$ 200,000	1,700,000
Partners' Capital Account, Return of Capital			$ 100,000
Payments for Advance to Affiliate	$ 800,000
Offshore Support Vessels [Member]
Schedule of Equity Method Investments [Line Items]
Number Of Equipments Acquired | equipment	17	6	7
Asset Impairment Charges	$ 120,800,000	$ 6,600,000
Offshore Support Vessels [Member] | MexMar [Member]
Schedule of Equity Method Investments [Line Items]
Number of Equipment Operated | equipment	15
Offshore Support Vessels [Member] | Sea-Cat Crewzer II [Member]
Schedule of Equity Method Investments [Line Items]
Number of Equipment Operated | equipment	2
Offshore Support Vessels [Member] | OSV Partners [Member]
Schedule of Equity Method Investments [Line Items]
Number of Equipment Operated | equipment	5
Number Of Equipments Acquired | equipment			2
Payments to Acquire Machinery and Equipment			$ 27,700,000
Offshore Support Vessels [Member] | Nautical Power [Member]
Schedule of Equity Method Investments [Line Items]
Number of Equipment Operated | equipment	1
Offshore Support Vessels [Member] | Sea Cat Crewzer [Member]
Schedule of Equity Method Investments [Line Items]
Number of Equipment Operated | equipment	2
Liftboats [Member] | Falcon Global [Member]
Schedule of Equity Method Investments [Line Items]
Number of Equipment Operated | equipment	2
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 3,800,000
Inland River Towboats [Member]
Schedule of Equity Method Investments [Line Items]
Number Of Equipments Acquired | equipment	2	9	1
Inland River Towboats [Member] | SCFCo Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Number Of Equipments Acquired | equipment			1
Inland River Dry Cargo Barges [Member]
Schedule of Equity Method Investments [Line Items]
Number Of Equipments Acquired | equipment	46	0	65
Inland River Dry Cargo Barges [Member] | SCFCo Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Number Of Equipments Acquired | equipment			20
U.S.-flag Harbor Tugs [Member]
Schedule of Equity Method Investments [Line Items]
Number Of Equipments Acquired | equipment	1	0	0
U.S.-flag Harbor Tugs [Member] | Trailer Bridge Inc [Member]
Schedule of Equity Method Investments [Line Items]
Related Party Transaction, Revenues from Transactions with Related Party	$ 3,000,000	$ 400,000	$ 2,000,000
Offshore Support Vessels [Member] | OSV Partners [Member]
Schedule of Equity Method Investments [Line Items]
Asset Impairment Charges	1,000,000
Offshore Support Vessels [Member] | Other Offshore Marine Services Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Asset Impairment Charges	$ 2,700,000	$ 2,000,000
SeaJon II [Member]
Schedule of Equity Method Investments [Line Items]
Number Of Equipments Acquired | equipment	1
Business Acquisition, Percentage of Voting Interests Acquired				50.00%
Payments to Acquire Businesses, Gross	$ 3,400,000
Subordinated Debt [Member] | VA&E [Member]
Schedule of Equity Method Investments [Line Items]
Advanced to joint ventures	$ 3,500,000				1,000,000
Long-term Debt [Member] | VA&E [Member]
Schedule of Equity Method Investments [Line Items]
Advanced to joint ventures					$ 1,100,000