Fair Value Measurements and Derivatives - Consolidated financial statements of fuel swaps dedesignated and immediately recognized into earnings (Details 3) - Reclassification out of Accumulated Other Comprehensive Income - Fuel Swaps - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss recognized in other expense	$ (179)	$ (4,716)	$ (271)	$ (4,716)
Amount reclassified from accumulated other comprehensive income (loss) into other income (expense)			$ 2,994	$ 10,000