Derivative Instruments (Narrative) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) contract	Apr. 30, 2015 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative (Gain) Loss	$ 2,800	$ 2,991	$ (132)
Derivative liability		121	7,050
Embedded derivative liabilities		1,200
Current derivative liability		1,040	298
Unrealized loss related to derivative instruments included in accumulated other comprehensive loss		0	3,700
Other Long-term Liabilities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative liability			3,000
Embedded derivative liabilities		100
Current Liabilities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Embedded derivative liabilities		$ 1,100
Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Yen denominated foreign forward exchange contract settled				$ 4,000
Foreign Exchange Contracts [Member] | Other Long-term Liabilities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative liability			4,000
Foreign Exchange Contracts [Member] | Current Liabilities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative liability			$ 100
Foreign Exchange Contract 1 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Number of forward purchase contracts | contract			3
Foreign Exchange Contract 2 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Number of forward purchase contracts | contract			2
Notional amount of forward purchase contracts			$ 900
Exchange rate			13.6007
Foreign Exchange Contract 3 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of forward purchase contracts			$ 900
Exchange rate			13.7503
Oslo Bulk AS [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Equity investee ownership interest		25.00%	25.00%
Minimum [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Embedded derivative liabilities		$ 800
Maximum [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Embedded derivative liabilities		$ 1,500
Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Yen denominated interest rate swap settled				$ 2,900
Interest Rate Swaps [Member] | Oslo Bulk AS [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized loss related to derivative instruments included in accumulated other comprehensive loss			$ 412