Derivative Instruments And Hedging Strategies (Recognized Gains (Losses) On Derivative Instruments Designated As Cash Flow Hedges) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax	$ 331,000	$ (195,000)
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax			0	(19,000)
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net			380,000	(690,000)
Interest Rate Swap Agreements [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax			380,000	(671,000)
Offshore Marine Services Joint Ventures [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Notional Amount	17,500,000		17,500,000
Offshore Marine Services Joint Ventures [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Fixed Interest Rate	1.48%		1.48%
Inland River Joint Venture [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Notional Amount	$ 38,800,000		$ 38,800,000
Inland River Joint Venture [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Lower Fixed Interest Rate Range	1.53%		1.53%
Derivative, Higher Fixed Interest Rate Range	4.16%		4.16%