Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2019

Asset Retirement Obligation Disclosure [Abstract]

Schedule of change in asset retirement obligation

During 2019 and 2018, our overall asset retirement obligation changed as follows (in thousands): 

	2019			2018
Beginning balance	$	394,323		$	363,956
Accretion	21,806			32,924
New obligations	103			14,162
Changes in estimates of existing obligations (1)	49,070			(8,054		)
Property dispositions/obligations settled	(6,093		)	(8,665		)
Ending balance	$	459,209		$	394,323

(1)

Changes in estimates of existing obligations are primarily due to the annual review process, which considers various factors including inflation rate, current estimates for removal costs, discount rates, and the estimated remaining life of assets. The increase in 2019 is primarily due to an increase in the inflation rate and a decrease in the discount rate. The decrease in 2018 is primarily due to a decrease in current estimates for onshore removal costs.