Asset Retirement Obligations (Tables)

3 Months Ended

Mar. 31, 2020

Asset Retirement Obligation Disclosure [Abstract]

Summary of Changes in Asset Retirement Obligations

The following table summarizes the changes in asset retirement obligations for the three months ended March 31, 2020:

Total asset retirement obligations at December 31, 2019	$	224,704
Accretion for the period	7,375
Sites added during the period	328
Revisions in estimated cash flows (1)	(1,938		)
Expenditures for the period	(4,696		)
Total asset retirement obligations at March 31, 2020	225,773
Less current portion	(36,314		)
Long-term portion	$	189,459

⁽¹⁾  The revisions in estimated cash flows resulted primarily from changes in mine plans.