Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 2,821	$ 2,162	$ 1,759
Net actuarial gains (losses) of defined benefit plans:
Adjustment, net of tax benefit (expense) of $25, ($60) and $29	(46)	105	(81)
Recognized within Net income, net of tax benefit (expense) of ($21), ($37) and ($104)	42	71	160
Prior service cost of defined benefit plans:
Adjustment, net of tax benefit (expense) of $0, $1 and $1	(1)	(3)	(2)
Recognized within Net income, net of tax benefit (expense) of $0, $2 and $0	0	(3)	0
Derivative instruments:
Change in fair value, net of tax benefit (expense) of $0, $0 and $1	0	0	(3)
Recognized within Net income, net of tax benefit (expense) of ($1), ($1) and $0	1	1	0
Available-for-sale investments:
Unrealized gains (losses), net of tax benefit (expense) of $0, $0 and ($1)	0	0	3
Other comprehensive income (loss), net of taxes	(4)	171	77
Total comprehensive income	$ 2,817	$ 2,333	$ 1,836