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Asset Retirement Obligations
 12 Months Ended
Dec. 31, 2019
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligations Asset Retirement Obligations
The table below summarizes the changes in our recorded asset retirement obligations (in thousands):
 
Year Ended December 31,
 
2019
 
2018
 
2017
Beginning balance
$
9,985

 
$
9,103

 
$
9,042

Obligations acquired
—

 
487

 
—

Accretion expense
331

 
395

 
369

Liabilities settled during period
(136
)
 
—

 
(308
)
Ending balance
$
10,180

 
$
9,985

 
$
9,103