Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	$ (2,765)	$ (2,513)
Other comprehensive loss before reclassifications	(219)	(11)
Amounts reclassified from accumulated other comprehensive income	27	53
Other comprehensive income (loss)	(192)	42
Balance at end of period	(2,957)	(2,471)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(1,781)	(1,828)
Other comprehensive loss before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income	23	32
Other comprehensive income (loss)	23	32
Balance at end of period	(1,758)	(1,796)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(980)	(658)
Other comprehensive loss before reclassifications	(206)	(9)
Amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income (loss)	(206)	(9)
Balance at end of period	(1,186)	(667)
Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(4)	(27)
Other comprehensive loss before reclassifications	(13)	(2)
Amounts reclassified from accumulated other comprehensive income	4	21
Other comprehensive income (loss)	(9)	19
Balance at end of period	$ (13)	$ (8)