Commitments and Contingencies - Commitments (Details) (USD $) In Millions, unless otherwise specified									3 Months Ended
	Sep. 30, 2013 aircraft	Sep. 30, 2013 Aircraft and Related Flight Equipment [Member]	Sep. 30, 2013 Reservation System Provider [Member]	Sep. 30, 2013 Airbus A320 Family [Member] aircraft	Sep. 30, 2013 Airbus A320, current model [Member] aircraft	Sep. 30, 2013 Airbus A321 [Member] aircraft	Sep. 30, 2013 Airbus A320 NEO [Member] aircraft	Sep. 30, 2013 Airbus A321 NEO [Member] aircraft	Jun. 30, 2012 Airbus A319 [Member] aircraft	Jun. 30, 2013 Airbus A319 [Member]	Sep. 30, 2013 V2500 SelectOne Engine [Member] aircraft_engine	Sep. 30, 2013 PurePower PW1100G-JM Engine [Member] aircraft_engine
Commitments and Contingencies Disclosure [Abstract]
Number of spare aircraft engines ordered (in aircraft engine)											6	9
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of Aircraft with Extended Leases (in aircraft)									14
Additional Lease Commitments due to Extended Aircraft Leases, Due 2017 and thereafter										$ 72.8
Number of Additional Aircraft Ordered (in aircraft)						20
Number of Aircraft Originally Ordered (in aircraft)				95
Number of Aircraft Whose Aircraft Type Was Converted						10		5
Number of aircraft ordered (in aircraft)				115	40	25	45	5
Number of Direct Leased Aircraft Ordered from a Third Party (in aircraft)							5
Number of Aircraft with Secured Financing Commitments Scheduled for Delivery (in aircraft)	10
Number of Aircraft without Secured Financing Commitments Scheduled for Delivery (in aircraft)	105
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Committed expenditures, remainder of 2013		136.0	0.9
Committed expenditures, 2014		412.0	3.9
Committed expenditures, 2015		794.0	3.9
Committed expenditures, 2016		640.0	3.9
Committed expenditures, 2017		816.0	3.9
Committed expenditures, 2018 and beyond		$ 2,743.0	$ 2.6