Financial Derivative Instruments (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative instrument
Gains (losses) on fuel derivatives recorded as Nonoperating income (expense)	$ (27,892,000)	$ 2,536,000	$ (28,506,000)	$ (10,931,000)
Derivatives Not Designated as Hedging Instruments | Fuel derivative contracts
Derivative instrument
Losses realized at settlement	(4,632,000)	(3,790,000)	(6,530,000)	(11,226,000)
Reversal of prior period unrealized amounts	56,000	4,278,000	(1,816,000)	5,472,000
Unrealized gains (losses) that will settle in future periods	(23,316,000)	2,048,000	(20,160,000)	(5,177,000)
Gains (losses) on fuel derivatives recorded as Nonoperating income (expense)	(27,892,000)	2,536,000	(28,506,000)	(10,931,000)
Derivatives Designated as Hedging Instruments | Interest rate derivative
Derivative instrument
Reclassified net gains (losses) from AOCI	(200,000)		(600,000)
Accumulated other comprehensive income (loss) expected to be reclassified to earnings in the next 12 months			(700,000)
Reclassification estimated time period			12 months
Derivatives Designated as Hedging Instruments | Foreign currency derivatives
Derivative instrument
Reclassified net gains (losses) from AOCI	1,300,000		6,500,000
Accumulated other comprehensive income (loss) expected to be reclassified to earnings in the next 12 months			$ 8,100,000
Reclassification estimated time period			12 months