Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2019

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Change in Asset Retirement Obligation

Asset retirement obligations (ARO) consists primarily of estimated costs of dismantlement, removal, site reclamation and similar activities associated with our oil and gas properties. Changes in ARO are as follows:

	Year Ended December 31,
(millions)	2019			2018
Asset Retirement Obligations, Beginning of Period	$	880		$	875
Liabilities Incurred	70			25
Liabilities Settled	(110		)	(345		)
Revisions of Estimates	(69		)	293
Reclassification to Liabilities Associated with Assets Held for Sale	—			(1		)
Accretion Expense	43			33
Asset Retirement Obligations, End of Period	$	814		$	880