Financial Instruments and Risk Management - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) aircraft derivative_instrument
Derivative [Line Items]
Unrealized gain (loss) on interest rate derivative instruments, net of deferred taxes of $0, $749, $0 and ($191)	$ 0	$ 1,238	$ 0	$ (356)
Unrealized gain (loss) on interest rate derivative instruments, tax	0	749	0	(191)
Accumulated other comprehensive loss	(1,455)		(1,455)		$ (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)		$ (1,500)
Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Unrealized gain (loss) on interest rate derivative instruments, net of deferred taxes of $0, $749, $0 and ($191)		(1,238)		400
Unrealized gain (loss) on interest rate derivative instruments, tax		$ 700		$ 200
Loss reclassified from AOCI into earnings	$ 88