Accumulated Other Comprehensive Loss (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reclassifications out of accumulated other comprehensive income (loss) by component
Total before tax	$ (323)	$ (394)	$ (654)	$ (899)
Income tax expense (benefit)	(130)	(125)	(258)	(332)
Net income	193	269	396	567
Amount reclassified from accumulated other comprehensive income (loss)
Reclassifications out of accumulated other comprehensive income (loss) by component
Net actuarial loss	(5)	(21)	(10)	(42)
Prior service cost	(8)	(1)	(13)	(2)
Total before tax	13	22	23	44
Income tax expense (benefit)	5	10	9	18
Insignificant items		(1)		(1)
Net income	$ (8)	$ (13)	$ (14)	$ (27)