We are required to record the estimated fair value of the liabilities relating to the future retirement of our long-lived assets (AROs). Our oil and natural gas wells are plugged and abandoned when the oil and natural gas reserves in those wells are depleted or the wells are no longer able to produce. The plugging and abandonment liability for a well is recorded in the period in which the obligation is incurred (at the time the well is drilled or acquired). None of our assets are restricted for purposes of settling these AROs. All of our AROs relate to plugging costs associated with our oil and gas wells.

The following table shows certain information about our AROs for the periods indicated:


	Nine Months Ended September 30,
	2011			2010
	(In thousands)
ARO liability, January 1:	$	69,265		$	56,404
Accretion of discount		2,598			2,138
Liability incurred ⁽¹⁾		12,674			2,901
Liability settled		(831	)		(622	)
Revision of estimates ⁽² ⁾		9,096			3,822

ARO liability, September 30:		92,802			64,643
Less current portion		2,074			1,617

Total long-term ARO liability	$	90,728		$	63,026

(1) Liability incurred in 2011 includes estimates for new wells acquired.

(2) Plugging liability estimates were revised upward in both 2011 and 2010 due to increases in the cost of services used to plug wells over the preceding years.