Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 798	$ 826	$ 2,150	$ 1,996
Net actuarial gains (losses) of defined benefit plans:
Adjustments	(33)	28	(43)	21
Recognized within Net income	13	17	40	38
Prior service cost of defined benefit plans:
Adjustments	20	0	20	0
Recognized within Net income	0	(1)	1	0
Derivative instruments:
Recognized within Net income	1	0	1	1
Other comprehensive income (loss)	1	44	19	60
Total comprehensive income	$ 799	$ 870	$ 2,169	$ 2,056