Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2012

Asset Retirement Obligations

Change in asset retirement obligations

The following schedule shows the change in our asset retirement obligations for 2012 and 2011 (dollars in millions):

	2012		2011
Asset retirement obligations at the beginning of year	$	280	$	329
Changes attributable to:
Accretion expense	19		19
Estimated cash flow revisions	58		(68		)
Asset retirement obligations at the end of year	$	357	$	280