	2012		2011

Federal coal lease obligations, current	$	63,191	$	102,198
Federal coal lease obligations, noncurrent		122,928		186,119

Total federal coal lease obligations	$	186,119	$	288,317

Our federal coal leases, as reflected in the consolidated balance sheets, consist of discounted obligations payable to the Bureau of Land Management of the U.S. Department of the Interior (the "BLM").

On May 11, 2011, we successfully won the lease sale of West Antelope II North ("WAII North") with a bid of $297.7 million, or approximately $0.85 per ton, based on the BLM's estimate of 350 million mineable tons. We submitted a payment for $59.5 million on May 11, 2011, and four additional payments in the same amount are payable annually on July 1, the date of the lease award, the first of which was made in 2012.

On June 15, 2011, we successfully won the lease sale of West Antelope II South ("WAII South") with a bid of $49.3 million, or approximately $0.875 per ton, based on the BLM's estimate of 56 million mineable tons. We submitted a payment for $9.9 million on June 15, 2011, and four additional payments in the same amount are payable annually on September 1, the date of the lease award, the first of which was made in 2012.

Accordingly, during the second quarter of 2011, we recognized $293.9 million of mineral rights in our long-term assets along with a corresponding liability of $224.5 million, representing the discounted amount of the future lease payment obligations. Interest is capitalized, resulting in a reduction of interest expense, as activities occur necessary to get these assets ready for their intended use, and generally will cease when all permits necessary to mine are received.

In addition to these obligations, the lease awards triggered updates to the ARO (see Note 13) and the Tax Agreement Liability (see Note 10).

As of December 31, we have federal coal lease payments, as follows (in thousands):

						2012				2011

Payment Dates	Annual Payment		Imputed Interest Rate			Carrying Value		Fair Value(1)		Carrying Value		Fair Value
August 1, 2008 - 2012	$	50,160		7.50	%		—		—		46,661		48,867
May 1, 2009 - 2013	$	9,620		8.70	%		8,852		9,532		16,998		18,517
July 1, 2011 - 2015	$	59,545		8.50	%		152,078		171,075		192,892		215,796
September 1, 2011 - 2015	$	9,862		8.50	%		25,189		28,196		31,766		35,293

						$	186,119	$	208,803	$	288,317	$	318,473

(1): The fair value of estimates for federal coal lease obligations were determined by discounting the remaining lease payments using a current estimate of the credit-adjusted, risk-free rate based on our current credit rating, which are considered Level 2 in the fair value hierarchy.

Year Ended December 31,

2013	$	79,027
2014		69,407
2015		69,407

Total		217,841
Less: imputed interest		31,722

Total principal payments		186,119
Less: current portion		63,191

Long-term federal coal leases payable	$	122,928

We recognize imputed interest on federal coal leases based on an estimate of the credit-adjusted, risk-free rate reflecting our estimated credit rating at the inception of the lease. Imputed interest on federal coal leases for the years ended December 31 was as follows (in thousands):

		2012			2011			2010

Imputed interest		$	20,406		$	19,619		$	11,673

Other long-term obligations consist of obligations incurred in connection with the acquisitions of land and mineral rights. At December 31, we had the following purchase obligations with parties other than the BLM (in thousands):

	2012	2011

Purchase obligations, total	$2,661	$6,567
Interest rate	6% - 8%	6% - 8%

The fair value of other long-term obligations approximated its carrying amount at December 31, 2012 and 2011.