Accumulated Other Comprehensive Income (Loss) (Reclassification out of AOCI) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	$ 293	$ (19)	$ 257	$ (54)
Net change in value	0	(1)	(2)	0
Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	5	13	12	12
Unrealized gain (loss) on investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	0	1	2	0
Income Tax Benefit (Expense) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	330	0	330	0
Prior Service Cost [Member] | Pension And Retiree Medical Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	(52)	(54)	(106)	(108)
Actuarial Loss [Member] | Pension And Retiree Medical Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	10	21	19	42
AA [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	290	(19)	255	(54)
Net change in value	2	(1)	0	0
Non-cash tax provision on sale of fuel hedging contracts	328		328
AA [Member] | Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	5	13	12	12
AA [Member] | Unrealized gain (loss) on investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net change in value	(2)	1	0	0
AA [Member] | Income Tax Benefit (Expense) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	328	0	328	0
AA [Member] | Prior Service Cost [Member] | Pension And Retiree Medical Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	(51)	(54)	(104)	(108)
AA [Member] | Actuarial Loss [Member] | Pension And Retiree Medical Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	10	21	19	42
Fuel Hedging Contract [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Non-cash tax provision on sale of fuel hedging contracts	330		330
Fuel Hedging Contract [Member] | AA [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Non-cash tax provision on sale of fuel hedging contracts	$ 328		$ 328