Segment Information (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment income	$ 619	$ (685)	$ 1,927	$ 812
Depreciation and amortization	(1,097)	(1,135)	(3,297)	(3,375)
Impairment of goodwill	0	(1,100)	0	(1,100)
Other unassigned operating expenses	(823)	(1,047)	(2,497)	(2,679)
Other income (expense), net	(320)	(320)	(974)	(918)
Income tax expense	(111)	(40)	(369)	(372)
Net income (loss)	188	(1,045)	584	(478)
Operating segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment income	2,103	2,178	6,458	6,743
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Other operating revenues	250	248	757	754
Depreciation and amortization	(1,097)	(1,135)	(3,297)	(3,375)
Impairment of goodwill	0	(1,100)	0	(1,100)
Other unassigned operating expenses	(637)	(876)	(1,991)	(2,210)
Other income (expense), net	(320)	(320)	(974)	(918)
Income tax expense	$ (111)	$ (40)	$ (369)	$ (372)