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Asset Retirement Obligations
 12 Months Ended
Dec. 31, 2015
Asset Retirement Obligation [Abstract]  
Asset Retirement Obligations
Asset Retirement Obligations

The Company's asset retirement obligations arise from the Federal Surface Mining Control and Reclamation Act of 1977 and similar state statutes, which require that mine property be restored in accordance with specified standards and an approved reclamation plan. The required reclamation activities to be performed are outlined in the Company's mining permits. These activities include reclaiming the pit and support acreage at surface mines, sealing portals at underground mines, and reclaiming refuse areas and slurry ponds.
The following table describes the changes to the Company's asset retirement obligation liability:
 
Year Ended December 31,
 
2015
 
2014
 
(In thousands)
Balance at January 1 (including current portion)
$
418,118

 
$
427,653

Accretion expense
33,680

 
32,909

Obligations of divested operations
(334
)
 
(30,684
)
Adjustments to the liability from changes in estimates
(28,570
)
 
627

Liabilities settled
(12,440
)
 
(12,387
)
Balance at December 31
$
410,454

 
$
418,118

Current portion included in accrued expenses
(13,795
)
 
(19,222
)
Noncurrent liability
$
396,659

 
$
398,896



As of December 31, 2015, the Company had $155.3 million in surety bonds outstanding, $485.5 million in self-bonding, and $11.2 million in letters of credit to secure reclamation bonding obligations.