Leases and Prepaid Maintenance Deposits - Operating Leases (Narrative) (Details) (USD $)	12 Months Ended					12 Months Ended							3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Prepaid expenses and other current assets	Dec. 31, 2012 Prepaid expenses and other current assets	Dec. 31, 2013 Aircraft leases	Dec. 31, 2013 Aircraft Minimum	Dec. 31, 2013 Aircraft Maximum	Dec. 31, 2013 Other leased equipment and property Maximum	Dec. 31, 2013 Spare engines aircraft_engine	Dec. 31, 2013 Spare engines Minimum	Dec. 31, 2013 Spare engines Maximum	Jun. 30, 2012 Airbus A319 aircraft
Operating Leased Assets [Line Items]
Operating leases, term							3 years	15 years	25 years		7 years	12 years
Total rental expense	$ 207,400,000	$ 172,400,000	$ 139,100,000
Rental expense charged to operations for aircraft and engine operating leases	169,737,000	143,572,000	116,485,000
Supplemental rent expense	5,200,000	2,000,000	1,500,000
Prepaid aircraft maintenance to lessors, total	220,700,000	198,500,000
Prepaid aircraft maintenance to lessors, current				59,200,000	76,100,000
Payments for contingent rent	$ 1,900,000	$ 2,000,000	$ 1,500,000
Number of aircraft and spare engines financed under operating leases						54				9
Number of aircraft and spare engines financed under operating leases with a variable rate						5
Number of aircraft with extended leases													14
Number of aircraft leaes available for renewal						3
Aircraft operating leases, renewal term						3 years
Aircraft operating leases, period before renewal						10 years