Supplemental Cash Flow Information Supplemental Cash Flow Information (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Other Significant Noncash Transactions [Line Items]
Common stock issued for employee benefit plans	$ 60	$ 7
Change in capital expenditures not paid	$ (16)	$ (43)