Asset Retirement Obligations

12 Months Ended

Dec. 31, 2017

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations

17. Asset Retirement Obligations

The following table presents the changes in asset retirement obligations.

	Year Ended December 31,
	2017			2016
Asset retirement obligations as of beginning of period	$	1,272		$	1,414
Liabilities incurred and assumed through acquisitions		40			27
Liabilities settled and divested		(68	)		(324	)
Revision of estimated obligation		(184	)		66
Accretion expense on discounted obligation		62			75
Foreign currency translation adjustment		30			14
Asset retirement obligations as of end of period		1,152			1,272
Less current portion		39			46
Asset retirement obligations, long-term	$	1,113		$	1,226

During 2017, Devon reduced its asset retirement obligations by $184 million primarily due to changes in the assumed inflation rate and retirement dates for its oil and gas assets.

During 2016, Devon reduced its asset retirement obligation by $287 million for those obligations that were assumed by purchasers of certain upstream U.S. assets.