Hedging - Foreign Currency and Fuel Derivatives Narrative (Details) (USD $)	6 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2014 Bunker fuel forward contracts
Derivative [Line Items]
Realized gain (loss) on foreign currency derivative instruments not designated as hedging instruments recorded in Net sales	$ (1,127,000)
Unrealized gains (losses) on foreign currency derivative instruments not designated as hedges recorded in Net sales	1,677,000
Amount of unrealized net losses on foreign currency cash flow hedging portfolio that would be reclassified to net income, if realized in the next twelve months		1,000,000
Maximum period for which the company locks in fuel purchase prices			3 years
Amount of unrealized net gains on bunker fuel hedging portfolio that would be reclassified to net income, if realized in the next twelve months			$ 1,000,000