Segment Information (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reconciliation from segment income to net income
Total segment income	$ 655	$ 715	$ 1,308	$ 1,497
Depreciation and amortization	(1,093)	(1,123)	(2,200)	(2,240)
Other unassigned operating expenses	(831)	(814)	(1,674)	(1,632)
Other income (expense), net	(332)	(321)	(654)	(598)
Income tax expense	(130)	(125)	(258)	(332)
Net income	193	269	396	567
Operating segments
Reconciliation from segment income to net income
Total segment income	2,170	2,235	4,355	4,563
Unallocated amount to segment
Reconciliation from segment income to net income
Other operating revenues	253	249	507	506
Depreciation and amortization	1,093	1,123	2,200	2,240
Other unassigned operating expenses	675	646	1,354	1,332
Other income (expense), net	(332)	(321)	(654)	(598)
Income tax expense	$ 130	$ 125	$ 258	$ 332