Financial Instruments and Risk Management - Narrative (Details) gal in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) aircraft derivative_instrument $ / gal gal	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) aircraft derivative_instrument $ / gal gal	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) $ / gal gal
Derivative [Line Items]
Federal excise tax				$ 9,300,000
Anticipated jet fuel consumption protected by hedges (in gallons) | gal	15.3		15.3		88.7
Anticipated jet fuel consumption protected by hedges (as a percent)	23.00%		23.00%		35.00%
Unrealized gain (loss) on interest rate derivative instruments, net of deferred tax expense (benefit) of ($320), $0, ($511) and $0	$ (553,000)	$ 0	$ (909,000)	0
Unrealized gain (loss) on interest rate derivative instruments, tax	(320,000)	$ 0	(511,000)	$ 0
Accumulated other comprehensive loss	$ (1,627,000)		$ (1,627,000)		$ (718,000)
Airbus A321 [Member] | 2015 [Member]
Derivative [Line Items]
Number of aircraft protected by interest rate derivatives schedule for delivery | aircraft	3		3
Interest Rate Swap [Member]
Derivative [Line Items]
Number of interest rate derivatives settled | derivative_instrument	6		6
Derivative, notional amount	$ 120,000,000		$ 120,000,000
Accumulated other comprehensive loss	(1,627,000)		(1,627,000)
Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Unrealized gain (loss) on interest rate derivative instruments, net of deferred tax expense (benefit) of ($320), $0, ($511) and $0	(553,000)		(909,000)
Unrealized gain (loss) on interest rate derivative instruments, tax	320,000		511,000
Loss reclassified from AOCI into earnings	25,300		25,000
Loss reclassified from AOCI into earnings, tax	$ 14,800		$ 15,000
Options Held [Member] | Fuel [Member]
Derivative [Line Items]
Derivative contract, weighted average ceiling price (in USD per gallon) | $ / gal	1.92		1.92		2.07