Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2020

Asset Retirement Obligation Disclosure [Abstract]

Change in asset retirement obligations

The following schedule shows the change in our asset retirement obligations for the nine months ended September 30, 2020 (dollars in thousands): 

	2020
Asset retirement obligations at January 1, 2020	$	657,218
Changes attributable to:
Accretion expense	29,454
Settlements	(5,611)
Estimated cash flow revisions	5,190
Asset retirement obligations at September 30, 2020	$	686,251