Taxes (Details 2) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Changes to company's unrecognized tax benefits
Balance at January 1		$ 3,552	$ 3,848	$ 3,071
Foreign currency effects		(27)	(25)	(58)
Additions based on tax positions taken in current year		154	354	276
Additions/reductions resulting from current-year asset acquisitions/sales		0	(22)	0
Additions for tax positions taken in prior years		218	37	1,164
Reductions for tax positions taken in prior years		(678)	(561)	(176)
Settlements with taxing authorities in current year		(5)	(50)	(320)
Reductions as a result of a lapse of the applicable statute of limitations		(172)	(29)	(109)
Balance at December 31		3,042	3,552	3,848
Income Tax Authority [Line Items]
Excise and similar taxes on products and merchandise		7,359	8,186	8,492
Total taxes other than on income	[1]	12,030	12,540	13,063
United States
Income Tax Authority [Line Items]
Excise and similar taxes on products and merchandise		4,426	4,633	4,792
Import duties and other levies		4	6	4
Property and other miscellaneous taxes		1,367	1,002	1,036
Payroll taxes		270	273	255
Taxes on production		157	349	333
Total taxes other than on income		6,224	6,263	6,420
International
Income Tax Authority [Line Items]
Excise and similar taxes on products and merchandise		2,933	3,553	3,700
Import duties and other levies		40	45	41
Property and other miscellaneous taxes		2,548	2,277	2,486
Payroll taxes		161	172	168
Taxes on production		124	230	248
Total taxes other than on income		$ 5,806	$ 6,277	$ 6,643

[1] Includes excise, value-added and similar taxes. $7,359; $8,186; $8,492.