Leases (Details)		3 Months Ended		12 Months Ended
		Dec. 31, 2015 USD ($) aircraft CapitalLeases	Sep. 30, 2013 USD ($)	Dec. 31, 2015 USD ($) aircraft CapitalLeases	Dec. 31, 2014 USD ($) CapitalLeases	Dec. 31, 2013 USD ($)	Jul. 09, 2012 aircraft
Capital Leases, Balance Sheet, Assets by Major Class, Net [Abstract]
Flight equipment		$ 435,000,000		$ 435,000,000	$ 214,000,000
Less: accumulated amortization		29,000,000		29,000,000	22,000,000
Total		406,000,000		406,000,000	$ 192,000,000
Capital Leased Assets [Line Items]
2016		46,000,000		46,000,000
2017		46,000,000		46,000,000
2018		45,000,000		45,000,000
2019		45,000,000		45,000,000
2020		44,000,000		44,000,000
Thereafter		209,000,000		209,000,000
Total minimum lease payments		435,000,000		435,000,000
Less amount representing interest		79,000,000		79,000,000
Present value of minimum lease payments		356,000,000		356,000,000
Less current portion		32,000,000		32,000,000
Long-term portion		$ 324,000,000		$ 324,000,000
Number of capital leased assets | CapitalLeases		28		28	16
Rental expense for operating leases				$ 909,000,000	$ 931,000,000	$ 997,000,000
Number of operating leased assets | aircraft		95		95
Subleases
2016		$ (103,000,000)		$ (103,000,000)
2017		(103,000,000)		(103,000,000)
2018		(102,000,000)		(102,000,000)
2019		(97,000,000)		(97,000,000)
2020		(78,000,000)		(78,000,000)
Thereafter		(66,000,000)		(66,000,000)
Total minimum lease payments		(549,000,000)		(549,000,000)
Operating leases
2016		557,000,000		557,000,000
2017		545,000,000		545,000,000
2018		474,000,000		474,000,000
2019		407,000,000		407,000,000
2020		307,000,000		307,000,000
Thereafter		1,529,000,000		1,529,000,000
Total minimum lease payments		3,819,000,000		3,819,000,000
2016		636,000,000		636,000,000
2017		624,000,000		624,000,000
2018		551,000,000		551,000,000
2019		479,000,000		479,000,000
2020		359,000,000		359,000,000
Thereafter		961,000,000		961,000,000
Total minimum lease payments		3,610,000,000		$ 3,610,000,000
Minimum
Capital Leased Assets [Line Items]
Renewal term				1 year
Maximum
Capital Leased Assets [Line Items]
Renewal term				5 years
Love Field Airport
Operating leases
2016		24,000,000		$ 24,000,000
2017		24,000,000		24,000,000
2018		25,000,000		25,000,000
2019		25,000,000		25,000,000
2020		26,000,000		26,000,000
Thereafter		634,000,000		634,000,000
Total minimum lease payments		$ 758,000,000		$ 758,000,000
B-717-200
Capital Leased Assets [Line Items]
Number of capital leased assets | aircraft							2
Number of operating leased assets | aircraft							76
Number of aircrafts subleased | aircraft							88
Number of aircraft delivered to sublessee | aircraft		87		87
RemainingNumberOfAircraftToBeDeliveredToSublessee | aircraft		1		1
Number of owned assets | aircraft							10
Lease terms for owned aircraft		7 years
Contingent rental payment due		$ 0		$ 0
Residual value of leased properties		0		0
Estimated Loss On Sublease			$ 137,000,000
Sublease transaction costs	[1]			48,000,000	86,000,000
Sublease Obligations		$ 18,000,000		18,000,000	63,000,000	$ 122,000,000
Interest expense related to accretion				(1,000,000)	(5,000,000)
Additional Estimated Loss on Sublease				$ 2,000,000	22,000,000
Grounding Loss on Sublease					$ 9,000,000
B-717-200 | Minimum
Capital Leased Assets [Line Items]
Sublease terms		3 years
B-717-200 | Maximum
Capital Leased Assets [Line Items]
Sublease terms		8 years
B-717-200 | Direct Financing Lease [Member]
Capital Leased Assets [Line Items]
Number of aircraft delivered to sublessee | aircraft		2		2
B-717-200 | Sales Type Lease [Member]
Capital Leased Assets [Line Items]
Number of aircraft delivered to sublessee | aircraft		9		9
B-717-200 | Operating Lease [Member]
Capital Leased Assets [Line Items]
Number of aircraft delivered to sublessee | aircraft		76		76

[1] Includes lease conversion cost payments