Impairments (Tables)

9 Months Ended

Sep. 30, 2013

Investments, Debt and Equity Securities [Abstract]

Details of Impairment of Long-Lived Assets Held and Used by Asset [Table Text Block]

A summary of our impairments of fixed assets by asset class and other charges for the Current Quarter, the Prior Quarter, the Current Period and the Prior Period is as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
	($ in millions)
Buildings and land	$	8	$	7	$	247	$	227
Drilling rigs and equipment	24		31		27		54
Gathering systems	21		—		22		—
Other	32		—		47		—
Total impairments of fixed assets and other	$	85	$	38	$	343	$	281