Impairments (Tables)

12 Months Ended

Dec. 31, 2018

Asset Impairment Charges [Abstract]

Summary of impairments of fixed assets

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