Commitments and Contingencies (Details) (USD $)	12 Months Ended				3 Months Ended
	Dec. 31, 2014 aircraft		Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2010
Airport Project [Line Items]
Assets constructed for others	$ 621,000,000		$ 453,000,000
Depreciation and amortization	938,000,000		867,000,000	844,000,000
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	56	[1]
Firm - 737NG 800 (in units)	19
Options - 737NG (in units)	35
Additional - 700 A/C (in units)	20
Firm - 737MAX (in units)	30
Firm - 738MAX (in units)	170	[2]
Options - 737MAX (in units)	191
Total	521
Aircraft
Long-term Purchase Commitment [Line Items]
Committed expenditures, 2015	836,000,000
Committed expenditures, 2016	1,200,000,000
Committed expenditures, 2017	1,200,000,000
Committed expenditures, 2018	1,000,000,000
Committed expenditures, 2019	1,100,000,000
Committed expenditures, 2020 and beyond	5,700,000,000
2015
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	0
Firm - 737NG 800 (in units)	19
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	16
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	0
Options - 737MAX (in units)	0
Total	35
2016
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	31
Firm - 737NG 800 (in units)	0
Options - 737NG (in units)	11
Additional - 700 A/C (in units)	4
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	0
Options - 737MAX (in units)	0
Total	46
2017
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	15
Firm - 737NG 800 (in units)	0
Options - 737NG (in units)	12
Additional - 700 A/C (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	14
Options - 737MAX (in units)	0
Total	41
2018
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	10
Firm - 737NG 800 (in units)	0
Options - 737NG (in units)	12
Additional - 700 A/C (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	13
Options - 737MAX (in units)	0
Total	35
2019
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	0
Firm - 737NG 800 (in units)	0
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Firm - 737MAX (in units)	15
Firm - 738MAX (in units)	10
Options - 737MAX (in units)	0
Total	25
2020
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	0
Firm - 737NG 800 (in units)	0
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Firm - 737MAX (in units)	14
Firm - 738MAX (in units)	22
Options - 737MAX (in units)	0
Total	36
2021
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	0
Firm - 737NG 800 (in units)	0
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Firm - 737MAX (in units)	1
Firm - 738MAX (in units)	33
Options - 737MAX (in units)	18
Total	52
2022
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	0
Firm - 737NG 800 (in units)	0
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	30
Options - 737MAX (in units)	19
Total	49
2023
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	0
Firm - 737NG 800 (in units)	0
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	24
Options - 737MAX (in units)	23
Total	47
2024
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	0
Firm - 737NG 800 (in units)	0
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	24
Options - 737MAX (in units)	23
Total	47
2025
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	0
Firm - 737NG 800 (in units)	0
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	0
Options - 737MAX (in units)	36
Total	36
2026
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	0
Firm - 737NG 800 (in units)	0
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	0
Options - 737MAX (in units)	36
Total	36
2027
Long-term Purchase Commitment [Line Items]
Firm - 737NG 700 (in units)	0
Firm - 737NG 800 (in units)	0
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	0
Options - 737MAX (in units)	36
Total	36
LAX
Airport Project [Line Items]
Expected total airport modernization project cost	525,000,000
Assets constructed for others	52,000,000
FLL
Airport Project [Line Items]
Expected total airport modernization project cost	295,000,000
DAL
Airport Project [Line Items]
Expected total airport modernization project cost	519,000,000
Municipal bonds issued					146,000,000	310,000,000
Number of gates with rights to occupy after completion	16
Assets constructed for others	504,000,000
Airport construction obligation	501,000,000
Depreciation and amortization	20,000,000
Property, Plant, and Equipment Useful Life	27 years
Property Plant And Equipment Percentage Cost To Residual Value Minimum	17.00%
HOU
Airport Project [Line Items]
Expected total airport modernization project cost	156,000,000
Assets constructed for others	$ 64,000,000
B-737-800
Airport Project [Line Items]
Number of Aircrafts Purchased	33
B-737-700
Airport Project [Line Items]
Number of Aircrafts Purchased	11
Number of aircrafts leased	11
B737-300
Airport Project [Line Items]
Number of aircrafts retired from service	3
B737-500
Airport Project [Line Items]
Number of aircrafts retired from service	2
B-717-200
Airport Project [Line Items]
Number of aircrafts removed from active service	66

[1] The Company has flexibility to substitute 737-800s in lieu of 737-700 firm orders.

[2] The Company has flexibility to substitute MAX 7 in lieu of MAX 8 firm orders beginning in 2019.