Equity, Income Tax Effects on Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Effects Related to Components of Other Comprehensive Income
Foreign currency translation adjustment, before-tax amount	$ (98)	$ 164	$ (122)
Pension and other postretirement benefits:
Net actuarial gain (loss) arising during the year, before-tax amount	367	(228)	(285)
Plan amendments, before tax amount	371
Prior service cost arising during the year, before tax amount		(9)	(4)
(Gain) loss reclassified into income related to:
Net actuarial loss, before-tax amount	57	34	14
Prior service credit, before-tax amount	(33)	(20)	(21)
Settlement, before-tax amount	1	12	4
Net gain (loss) on pension and other postretirement benefits, before tax amount	763	(211)	(292)
Derivative instruments designated and qualifying as cash flow hedges:
Net gain (loss) arising during the year, before-tax amount	(4)	45	32
Net (gain) loss reclassified into income, before-tax amount	2	(73)	(3)
Net gain (loss) on derivative instruments designated and qualifying as cash flow hedges, before-tax amount	(2)	(28)	29
Other comprehensive income (loss) before tax amount	663	(75)	(385)
Foreign currency translation adjustment, tax expense (benefit)	0	0	0
Pension and other postretirement benefits:
Net actuarial gain (loss) arising during the year, tax expense (benefit)	125	(79)	(100)
Plan amendments, tax benefit	130
Prior service cost, tax benefit		(3)	(1)
(Gain) loss reclassified into income related to:
Amortization of net actuarial loss, tax expense	20	12	4
Amortization of prior service credit, tax benefit	(12)	(7)	(7)
Settlement, tax expense	0	0	1
Net gain (loss) on pension and other postretirement benefits, tax expense (benefit)	263	(77)	(103)
Derivative instruments designated and qualifying as cash flow hedges:
Net gain (loss) arising during the year, tax expense (benefit)	(2)	16	11
Net (gain) loss reclassified into income, tax expense (benefit)	1	(26)	(1)
Net gain (loss) on cash flow hedges, tax expense (benefit)	(1)	(10)	10
Other comprehensive income (loss) tax expense (benefit)	262	(87)	(93)
Foreign currency translation adjustment, net	(98)	164	(122)
Pension and other postretirement benefits:
Net actuarial gain (loss) arising during the year, net	242	(149)	(185)
Plan amendments, net	241
Prior service cost, net		(6)	(3)
(Gain) loss reclassified into income related to:
Amortization of net actuarial loss, net	37	22	10
Amortization of prior service credit, net	(21)	(13)	(14)
Settlement, net	1	12	3
Net gain (loss) on pension and other postretirement benefits, net	(500)	134	189
Derivative instruments designated and qualifying as cash flow hedges:
Net gain (loss) arising during the year, net	(2)	29	21
Net (gain) loss reclassified into income, net	1	(47)	(2)
Net gain (loss) on cash flow hedges, net	(1)	(18)	19
Other comprehensive income (loss)	$ 401	$ 12	$ (292)