Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 3,595	$ 2,986	$ 2,821
Net actuarial gains (losses) of defined benefit plans:
Adjustment, net of tax benefit (expense) of $6, $36 and $25	(43)	(74)	(46)
Recognized within Net income, net of tax benefit (expense) of ($25), ($25) and ($21)	51	53	42
Prior service (cost) credit of defined benefit plans:
Adjustment, net of tax benefit (expense) of $0, ($11) and $0	0	20	(1)
Recognized within Net income, net of tax benefit (expense) of $2, $0 and $0	(3)	0	0
Derivative instruments:
Recognized within Net income, net of tax benefit (expense) of $0, ($1) and ($1)	1	1	1
Other comprehensive income (loss), net of taxes	6	0	(4)
Total comprehensive income	$ 3,601	$ 2,986	$ 2,817