Investments, At Equity, And Advances To 50% Or Less Owned Companies (Narrative) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Apr. 30, 2018
Schedule Of Equity Method Investments [Line Items]
Proceeds from Sale of Equity Method Investments	$ 78,015	$ 0
RF Vessel Holdings [Member]
Schedule Of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions	900
Golfo de Mexico [Member]
Schedule Of Equity Method Investments [Line Items]
Partners' Capital Account, Contributions	2,100
SCFCo Holdings [Member]
Schedule Of Equity Method Investments [Line Items]
Proceeds from Collection of Advance to Affiliate	(2,000)
Outstanding Working Capital Advances At End Of Period	30,000
Hawker Pacific Airservices Limited [Member]
Schedule Of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage			34.20%
Proceeds from Sale of Equity Method Investments	78,000
Equity Method Investment, Realized Gain (Loss) on Disposal	53,900
VA&E [Member]
Schedule Of Equity Method Investments [Line Items]
Proceeds from Collection of Advance to Affiliate	(5,400)
Outstanding Working Capital Advances At End Of Period	7,200
Line of Credit Facility, Maximum Borrowing Capacity	3,500
Proceeds from Unsecured Lines of Credit	5,400
Other Corporate Joint Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Proceeds from Collection of Advance to Affiliate	(400)
Outstanding Working Capital Advances At End Of Period	2,000
Subordinated Debt [Member] | VA&E [Member]
Schedule Of Equity Method Investments [Line Items]
Outstanding Working Capital Advances At End Of Period	$ 3,500