Derivative Instruments - Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Realized (losses) gains	$ 382	$ (10,643)	$ (9,790)
Unrealized gains (losses)	937	9,679	8,193
Total realized and unrealized gain (loss) on derivatives	1,319	(964)	(1,597)
Interest Rate Swap Agreements
Derivative [Line Items]
Realized (losses) gains	(994)	(12,797)	(9,790)
Unrealized gains (losses)	2,099	13,681	7,686
Time-charter Swap Agreement
Derivative [Line Items]
Realized (losses) gains	1,106	2,154	0
Unrealized gains (losses)	(875)	875	0
Forward freight agreements
Derivative [Line Items]
Realized (losses) gains	270	0	0
Stock Purchase Warrant
Derivative [Line Items]
Realized (losses) gains	0	0	0
Unrealized gains (losses)	$ (287)	$ (4,877)	$ 507

Derivative instruments not designated as hedging instruments realized gain (loss) net.

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- Definition

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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