Changes in Accumulated Other Comprehensive Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at January 1			$ (4,291)
Components of Other Comprehensive Income (Loss):
Other Comprehensive Gain, Net of Tax	$ 118	$ 129	259	$ 208
Balance at June 30	(4,032)		(4,032)
Income tax expense	(607)	$ 755	(1,611)	$ 1,060
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at January 1			(4,291)
Components of Other Comprehensive Income (Loss):
Before Reclassifications			15
Reclassifications			244
Other Comprehensive Gain, Net of Tax			259
Balance at June 30	(4,032)		(4,032)
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at January 1			(140)
Components of Other Comprehensive Income (Loss):
Before Reclassifications			2
Reclassifications			0
Other Comprehensive Gain, Net of Tax			2
Balance at June 30	(138)		(138)
Unrealized Holding Gains (Losses) on Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at January 1			(29)
Components of Other Comprehensive Income (Loss):
Before Reclassifications			10
Reclassifications			0
Other Comprehensive Gain, Net of Tax			10
Balance at June 30	(19)		(19)
Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at January 1			(2)
Components of Other Comprehensive Income (Loss):
Before Reclassifications			0
Reclassifications			0
Other Comprehensive Gain, Net of Tax			0
Balance at June 30	(2)		(2)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at January 1			(4,120)
Components of Other Comprehensive Income (Loss):
Before Reclassifications			3
Reclassifications			244
Other Comprehensive Gain, Net of Tax			247
Balance at June 30	$ (3,873)		(3,873)
Defined Benefit Plans [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Components of Other Comprehensive Income (Loss):
Employee benefits reclassification component, included in employee benefit costs			392
Income tax expense			$ 148