Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 696	$ 683	$ 1,352	$ 1,170
Net actuarial gains (losses) of defined benefit plans:
Adjustments	0	(5)	(10)	(7)
Recognized within Net income	17	11	27	21
Prior service cost of defined benefit plans:
Recognized within Net income	0	1	1	1
Derivative instruments:
Recognized within Net income	0	1	0	1
Other comprehensive income (loss)	17	8	18	16
Total comprehensive income	$ 713	$ 691	$ 1,370	$ 1,186