Summary of Significant Accounting Policies Income Statement Impact of Accounting Policy Change (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Change in Accounting Principle [Line Items]
Cost of goods sold and other operating charges	$ 7,105	$ 6,816
Income from continuing operations before income taxes	1,774	1,801
Provision for income taxes on continuing operations	387	392
Income from continuing operations after income taxes	1,387	1,409
Income from discontinued operations after income taxes	1,968	95
Net income	3,355	1,504
As Reported [Member]
Change in Accounting Principle [Line Items]
Cost of goods sold and other operating charges	7,105	6,816
Income from continuing operations before income taxes	1,774	1,801
Provision for income taxes on continuing operations	387	392
Income from continuing operations after income taxes	1,387	1,409
Income from discontinued operations after income taxes	1,968	95
Net income	3,355	1,504
As reported under LIFO [Member]
Change in Accounting Principle [Line Items]
Cost of goods sold and other operating charges	7,116	6,822
Income from continuing operations before income taxes	1,763	1,795
Provision for income taxes on continuing operations	384	392
Income from continuing operations after income taxes	1,379	1,403
Income from discontinued operations after income taxes	1,968	97
Net income	3,347	1,500
Impact of change in accounting principle [Member]
Change in Accounting Principle [Line Items]
(Decrease) Increase to Cost of Goods Sold and Other Operating Charges	(11)	(6)
(Decrease) Increase to Income From Continuing Operations Before Income Taxes	11	6
(Decrease) Increase to Provision for Income Taxes on Continuing Operations	3	0
(Decrease) Increase to Income from Continuing Operations after Income Taxes	8	6
(Decrease) Increase to Income From Discontinued Operations After Taxes	0	(2)
(Decrease) Increase to Net Income	$ 8	$ 4