Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2015

Asset Retirement Obligation Disclosure [Abstract]

Changes in asset retirement obligations

Changes in our asset retirement obligations were as follows (in thousands):

	December 31,
	2015		2014		2013
Balance as of beginning of year	$	975	$	931	$	889
Accretion expense	46		44		42
Balance as of end of year	$	1,021	$	975	$	931