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Change in Accounting Estimate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019	Dec. 31, 2018	Jan. 01, 2018
Retained Earnings (Accumulated Deficit)	$ 13,832			$ 15,967
Assets constructed for others	1,543			1,768
Accounting Standards Update 2017-07
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption	14	$ 12
Reclassification from Other operating expenses to be offset against Passenger revenues | Adjustments for New Accounting Standards Update 2014-09
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption	40
Restatement Adjustment
Assets constructed for others			$ 1,500
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability			1,400
Restatement Adjustment | Adjustments for New Accounting Standards Update 2014-09
Retained Earnings (Accumulated Deficit)	(789)
Restatement Adjustment | Accumulated other comprehensive income (loss) | Adjustments for New Accounting Standards Update 2014-09
Retained Earnings (Accumulated Deficit)					$ 20
DAL
Assets constructed for others	$ 543			545
Municipal Bonds Principal Remaining				$ 416
DAL | Restatement Adjustment
Municipal Bonds Principal Remaining			450
Aircraft | Restatement Adjustment
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability			700
Aircraft | Other Assets
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability			$ 200

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