Income Taxes (Narrative) (Details)	3 Months Ended		12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) item $ / T	Dec. 31, 2014 USD ($)	Dec. 31, 2012 USD ($)
Income Taxes [Line Items]
Deferred tax assets, valuation allowance	$ 18,493,000		$ 18,493,000	$ 13,936,000
Daily notional shipping income per 100 tons of the net tonnage of the vessel in excess of 25000 net tons			$ 0.20
Daily notional shipping income per 100 tons of the net tonnage of the vessel up to 25000 net tons | $ / T			0.40
Base quantity for calculation of daily notional shipping income | item			100
Corporate tax rate			35.00%	35.00%
Deferred gain on disposal				$ 93,900,000	$ 79,300,000
Qualified replacement property acquired		$ 45,600,000
Deferred gain from disposition of qualifying vessels remaining amount			$ 16,400,000
Increase (decrease) in valuation allowance			4,600,000
Income tax current recognition of earnings of foreign subsidiaries			2,000,000	2,500,000
Provision for income taxes			439,000	10,429,000
Foreign income taxes			0	0
Alternative minimum tax exposure amount	5,425,000		5,425,000	5,179,000
Deferred tax asset on unrecognized tax benefits related to restricted stock units	312,000		312,000
Loss before taxes and equity in net income of unconsolidated entities			(175,205,000)	(44,280,000)
Replacement Before December 31, 2015 [Member]
Income Taxes [Line Items]
Qualified replacement property acquired			25,000,000
Replacement Years of 2015 [Member]
Income Taxes [Line Items]
Deferred gain on disposal	17,300,000		17,300,000
Replacement Years of 2018 [Member]
Income Taxes [Line Items]
Deferred gain on disposal	7,700,000		7,700,000
Acquisition of Qualified Replacement Property [Member]
Income Taxes [Line Items]
Deferred tax liability		12,500,000
Controlled Foreign Corporations [Member]
Income Taxes [Line Items]
Increase (decrease) in valuation allowance		(5,300,000)
Deferred tax liability		$ 5,300,000
Tonnage Tax [Member]
Income Taxes [Line Items]
Provision for income taxes			54,000	52,000
Restricted Stock Unit Adjustments [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	1,600,000		1,600,000
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	59,400,000		59,400,000	49,000,000
Alternative minimum tax exposure amount	5,400,000		5,400,000
Net operating loss carryforwards generated during period			26,100,000
Federal [Member] | Restricted Stock Unit Adjustments [Member]
Income Taxes [Line Items]
Deferred tax asset on unrecognized tax benefits related to restricted stock units	300,000		300,000
Increase (decrease) to net operating loss	700,000
State [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	42,800,000		42,800,000	$ 31,300,000
Net operating loss carryforwards generated during period			11,500,000
Foreign [Member]
Income Taxes [Line Items]
Tax credits that are expected to be utilized on federal return			0
Net operating loss carryforwards	$ 4,000,000		$ 4,000,000
Minimum [Member] | Federal [Member]
Income Taxes [Line Items]
Expiration period			2025
Minimum [Member] | State [Member]
Income Taxes [Line Items]
Expiration period			2025
Maximum [Member] | Federal [Member]
Income Taxes [Line Items]
Expiration period			2035
Maximum [Member] | State [Member]
Income Taxes [Line Items]
Expiration period			2035