XML 47 R36.htm IDEA: XBRL DOCUMENT v3.7.0.1
Asset Retirement Obligations (Details)
$ in Thousands
3 Months Ended
Mar. 31, 2017
USD ($)
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]  
Asset retirement obligations, beginning of period $ 7,226
Liabilities assumed 0
Liabilities incurred 274
Liabilities settled (29)
Accretion expense 114
Revision of estimated liabilities 0
Asset retirement obligations, end of period $ 7,585