Recently Issued Accounting Standards - Schedule of Adoption of ASC 606 and Expected Impact (Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid expenses and other	$ 973	$ 1,071	[1]
Total current assets	8,671	7,133	[1]
Total assets	44,837	42,346	[1]
Advance ticket sales	5,193	3,940	[1]
Frequent flyer deferred revenue	2,275	2,192	[1]
Other	585	576	[1]
Total current liabilities	13,684	12,763	[1]
Frequent flyer deferred revenue - long-term	2,712	2,591	[1]
Deferred income taxes	639	204	[1]
Total other liabilities and deferred credits	8,350	8,150	[1]
Retained earnings	6,203	4,549	[1]
Total stockholders' equity	9,469	8,734	[1]
Total liabilities and stockholders' equity	$ 44,837	42,346	[1]
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid expenses and other		1,051
Total current assets		7,113
Total assets		42,326
Advance ticket sales		3,876
Frequent flyer deferred revenue		2,176
Other		569
Total current liabilities		12,676
Frequent flyer deferred revenue - long-term		2,565
Deferred income taxes		225
Total other liabilities and deferred credits		8,145
Retained earnings		4,621
Total stockholders' equity		8,806
Total liabilities and stockholders' equity		42,326
Restatement Adjustment | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid expenses and other		20
Total current assets		20
Total assets		20
Advance ticket sales		64
Frequent flyer deferred revenue		16
Other		7
Total current liabilities		87
Frequent flyer deferred revenue - long-term		26
Deferred income taxes		(21)
Total other liabilities and deferred credits		5
Retained earnings		(72)
Total stockholders' equity		(72)
Total liabilities and stockholders' equity		$ 20

[1] Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606). See Note 1 to the financial statements contained in Part I, Item 1 of this report for additional information.