Commitments And Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 defendant plaintiff item	Dec. 31, 2013	Jan. 06, 2015	Jun. 26, 2014 item
Commitments And Contingencies [Line Items]
Deposit reclassified to current receivable	$ 3,900,000
Interest accrued on receivable from customer	300,000
Number of vessels owned with commitments	22
Estimated lawsuit insurance coverage claims	352,000
Reserves for lawsuit claims	352,000	299,000
Insurance policies with deductibles, minimum amount per claim	1,500
Insurance policies with deductibles, maximum amount per claim	25,000
Number of plaintiffs	10
Number of defendants	40
Subsequent Event [Member]
Commitments And Contingencies [Line Items]
Deposit and interest collected			4,200,000
U.S. Customs And Border Protection [Member]
Commitments And Contingencies [Line Items]
Number of affiliates that allegedly failed to properly report the importation of spare parts consumed by vessels				2
Amount of proposed duty				2,100,000
Amount of proposed penalty on assessment				$ 8,400,000
Waterman [Member]
Commitments And Contingencies [Line Items]
Number of defendants	1