Leases (Narrative) (Details) (USD $)	1 Months Ended	12 Months Ended				0 Months Ended				12 Months Ended						12 Months Ended
	Nov. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2015 Scenario, Forecast [Member]	Nov. 27, 2012 BMO Harris Equipment Finance Company [Member]	Nov. 27, 2012 Capital Source Bank [Member]	Dec. 27, 2012 BB&T Equipment Finance [Member]	Feb. 22, 2012 Wells Fargo Bank Northwest [Member]	Dec. 31, 2013 New York Office [Member]	Dec. 31, 2013 Shanghai Office [Member]	Dec. 31, 2013 Tampa [member]	Jun. 30, 2013 Property Subject to Operating Lease [Member]	Dec. 31, 2013 Mobile Corporate Office Lease [Member]	Dec. 31, 2013 Mobile Corporate Office Lease [Member] Leasehold Improvements [Member]	Dec. 31, 2013 Mobile Corporate Office Lease [Member] Minimum [Member]	Dec. 31, 2013 Mobile Corporate Office Lease [Member] Maximum [Member]
Leases [Line Items]
Vessels, gross		$ 582,416,000	$ 525,172,000										$ 16,200,000
Sale leaseback, gross proceeds						32,000,000	31,000,000	32,000,000	59,000,000
Repayment of debt from proceeds of sale and leaseback transaction			(54,500,000)
Lease term						7 years	6 years	6 years
Gain on sale-leaseback						8,000,000	11,700,000		14,900,000
Sale-leaseback net proceeds	63,000,000
Office space lease agreement term		20 years								10 years	2 years	5 years
Early termination operating lease term																10 years	15 years
Leasehold Improvements		26,348,000	26,348,000							503,000				730,000
Incentive from Lessor															1,400,000
Lease termination expense					3,000,000
Rent expense		$ 20,000,000	$ 11,200,000	$ 13,600,000
Sale Leaseback Transaction Lease Term						7 years	6 years	6 years