Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2018

Asset Retirement Obligation Disclosure [Abstract]

Changes to and Maturity of Asset Retirement Obligations

The following table describes changes to and maturity of our asset retirement obligations:

	2018			2017
	(In millions)
Balance at January 1	$	801		$	2,128
Liabilities incurred		68			62
Liabilities settled or disposed of		(46	)		(1,464	)
Accretion expense		37			97
Revisions of estimated liabilities		1			(54	)
Foreign currency remeasurement		(4	)		32
Balance at December 31	$	857		$	801
Total Asset Retirement Obligations at December 31:
Current portion of asset retirement obligations	$	116		$	48
Long-term asset retirement obligations		741			753
Total at December 31	$	857		$	801