Impairments (Tables)

12 Months Ended

Dec. 31, 2018

Asset Impairment Charges [Abstract]

Summary of impairments

A summary of our impairments of fixed assets by asset class and other charges for the years ended December 31, 2018, 2017 and 2016 is as follows:

	Years Ended December 31,
	2018		2017		2016
	($ in millions)
Natural gas compressors	$	45	$	—	$	21
Barnett Shale exit costs	—		—		284
Devonian Shale exit costs	—		—		142
Gathering systems	—		—		3
Buildings and land	4		5		11
Other	4		—		—
Total impairments of fixed assets and other	$	53	$	5	$	461

A summary of our impairments of oil and natural gas properties for the years ended December 31, 2018, 2017 and 2016 is as follows:

	Years Ended December 31,
	2018		2017		2016
	($ in millions)
Impairments due to lower forecasted commodity prices	$	23	$	27	$	73
Impairments due to reduction in future development(a)	—		560		—
Impairments due to anticipated sale	55		222		29
Total impairments of oil and natural gas properties	$	78	$	809	$	102

(a) The impairment was the result of an updated development plan in 2017, which included a removal of PUDs from properties in the process of being divested in the Mid-Continent operating area.