Financial Instruments and Risk Management - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) aircraft derivative_instrument
Derivative [Line Items]
Unrealized loss on interest rate derivative instruments, net of deferred tax benefit of $0 and $940	$ 0	$ (1,594)
Unrealized gain (loss) on interest rate derivative instruments, tax	0	(940)
Accumulated other comprehensive loss	(1,511)		$ (1,546)
Airbus A321 [Member] | 2015 [Member]
Derivative [Line Items]
Number of aircraft protected by interest rate derivatives schedule for delivery | aircraft			3
Commodity Option [Member]
Derivative [Line Items]
Payments of Derivative Issuance Costs		2,100
Interest Rate Swap [Member]
Derivative [Line Items]
Number of interest rate derivatives settled | derivative_instrument			6
Accumulated other comprehensive loss	(1,500)
Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Unrealized loss on interest rate derivative instruments, net of deferred tax benefit of $0 and $940		1,600
Unrealized gain (loss) on interest rate derivative instruments, tax		$ 900
Loss reclassified from AOCI into earnings	$ 100