Commitments and Contingencies - Commitments (Details) ft² in Thousands	1 Months Ended		6 Months Ended
	Sep. 30, 2015 ft² a extension_option	Jul. 31, 2015 USD ($) aircraft seat	Jun. 30, 2016 USD ($) aircraft_engine aircraft
Aircraft [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Operating leases, lessee, number of leased assets | aircraft			58
Spare Engines [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Operating leases, lessee, number of leased assets | aircraft_engine			11
Hangar Facility [Member] | Operating Lease [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Area of land, hangar site | a	10
Area of hangar facility | ft²	126
Operating lease, initial term	30 years
Operating lease, number of extension options | extension_option	2
Operating lease, extension term	10 years
Estimated future project costs			$ 32,000,000
Aircraft [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of delivered aircraft with secured debt financing commitments | aircraft			8
Number of Previously Leased Aircraft Purchased | aircraft			3
Property and equipment, useful life			25 years
Property and equipment, salvage value percentage			10.00%
Airbus A320 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of aircraft held | aircraft			87
Airbus [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Costs to reconfigure aircraft seating		$ 600,000
Airbus [Member] | A320 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of aircraft reconfigured for increased seating capacity | aircraft		40
Airbus [Member] | A320 [Member] | Minimum [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of aircraft seats | seat		178
Airbus [Member] | A320 [Member] | Maximum [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of aircraft seats | seat		182
Aircraft and Related Flight Equipment [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation, Due in Remainder of Fiscal Year			$ 209,000,000
Unrecorded Unconditional Purchase Obligation, Due in 2017			668,000,000
Unrecorded Unconditional Purchase Obligation, Due in 2018			650,000,000
Aircraft with Increased Seating Capacity [Member] | Airbus [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation, Due in Remainder of Fiscal Year			6,600,000
Unrecorded Unconditional Purchase Obligation, Due in 2017			8,300,000
Unrecorded Unconditional Purchase Obligation, Due after 2017			0
Reservation System and Advertising Media [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation, Due in Remainder of Fiscal Year			2,600,000
Unrecorded Unconditional Purchase Obligation, Due in 2017			4,300,000
Unrecorded Unconditional Purchase Obligation, Due in 2018			2,800,000
Unrecorded Unconditional Purchase Obligation, thereafter			$ 0