Income Taxes (Tables)

9 Months Ended

Sep. 30, 2013

Table Text Block [Abstract]

Schedule of Income Taxes and Effective Tax Rate

 The following summarizes income tax expense (benefit) and effective tax rates:

	Three Months Ended   September 30,						Nine Months Ended   September 30,
millions except percentages	2013			2012			2013			2012
Income tax expense (benefit)	$	240		$	248		$	1,263		$	764
Effective tax rate	52		%	64		%	43		%	25		%