Asset Retirement Obligation (Tables)

12 Months Ended

Dec. 31, 2012

Assets Retirement Obligation [Abstract]

Schedule of changes in our asset retirement liability

The following table describes changes in our asset retirement liability during each of the years ended December 31, 2012 and 2011. The ARO liability in the table below includes amounts classified as both current and long-term at December 31, 2012 and 2011.

	North America Years Ended December 31				South America Years Ended December 31
	2012		2011		2012			2011
ARO liability at January 1	$	7,320	$	5,481	$	34,099		$	9,960
Accretion expense		552		1,839		372			14,607
Liabilities incurred from drilling		—		—		—			9,532
Liabilities settled—assets sold		—		—		(34,471	)		—
Changes in estimates		—		—		—			—
ARO liability at December 31,	$	7,872	$	7,320	$	—		$	34,099