Asset Retirement Obligations

12 Months Ended

Dec. 31, 2011

Asset Retirement Obligations [Abstract]

Asset Retirement Obligations

14.  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
	2011	2010
	(In thousands)
Balance at January 1 (including current portion)	$  343,119	$  310,409
Accretion expense	33,601	26,615
Obligations incurred or acquired	115,019	—
Adjustments to the liability from changes in estimates	11,176	8,934
Liabilities settled	(29,012)	(2,839)
Balance at December 31	$  473,903	$  343,119
Current portion included in accrued expenses	(27,119)	(8,862)
Noncurrent liability	$  446,784	$  334,257

Liabilities settled of $29.0 million in 2011 related to reclamation activities at the Black Thunder mining complex related to a pit acquired with the Jacobs Ranch operations in 2009.

As of December 31, 2011, the Company had $263.0 million in surety bonds outstanding and $420.5 million in self-bonding to secure reclamation obligations.